feat(diary): 添加发现页 Discover API — 每日灵感/热门标签/精选模板/专家日记

新增 DiscoverService 并发聚合 4 个数据区:
- daily_inspiration: MD5 哈希确定性日更推荐，匿名作者名
- hot_topics: 标签频率统计 Top 8
- featured_templates: 官方模板最多 6 个
- expert_diaries: 评论数热度排序，去重最多 5 位作者

GET /api/v1/diary/discover + utoipa 文档 + diary.journal.read 权限守卫

crates/erp-diary/src/dto.rs

@@ -380,6 +380,51 @@ pub struct TemplateResp {
     pub is_free: bool,
 }
 
+// ========== 发现页 ==========
+
+/// 发现页聚合响应 — 一次返回全部板块数据
+#[derive(Debug, Serialize, ToSchema)]
+pub struct DiscoverResp {
+    /// 每日推荐（无共享日记时为 null）
+    pub daily_inspiration: Option<InspirationItem>,
+    /// 热门话题（标签频率 TOP 8）
+    pub hot_topics: Vec<TagCount>,
+    /// 精选模板（官方模板）
+    pub featured_templates: Vec<TemplateResp>,
+    /// 达人日记（不同作者最近共享日记）
+    pub expert_diaries: Vec<ExpertDiaryItem>,
+}
+
+/// 每日推荐条目
+#[derive(Debug, Serialize, ToSchema)]
+pub struct InspirationItem {
+    pub journal_id: uuid::Uuid,
+    pub title: String,
+    pub author_name: String,
+    pub mood: String,
+    pub date: chrono::NaiveDate,
+}
+
+/// 热门话题
+#[derive(Debug, Serialize, ToSchema)]
+pub struct TagCount {
+    pub tag: String,
+    pub count: i64,
+}
+
+/// 达人日记条目
+#[derive(Debug, Serialize, ToSchema)]
+pub struct ExpertDiaryItem {
+    pub journal_id: uuid::Uuid,
+    pub title: String,
+    pub author_id: uuid::Uuid,
+    pub author_name: String,
+    pub author_emoji: String,
+    pub content_preview: String,
+    pub like_count: i64,
+    pub created_at: chrono::DateTime<chrono::Utc>,
+}
+
 /// 成就响应
 #[derive(Debug, Serialize, ToSchema)]
 pub struct AchievementResp {

crates/erp-diary/src/handler/discover_handler.rs

@@ -0,0 +1,40 @@
+// 发现页 API 处理器
+
+use axum::extract::{Extension, FromRef, State};
+use axum::response::Json;
+
+use erp_core::error::AppError;
+use erp_core::rbac::require_permission;
+use erp_core::types::{ApiResponse, TenantContext};
+
+use crate::dto::DiscoverResp;
+use crate::service::discover_service::DiscoverService;
+use crate::state::DiaryState;
+
+#[utoipa::path(
+    get,
+    path = "/api/v1/diary/discover",
+    responses(
+        (status = 200, description = "成功", body = ApiResponse<DiscoverResp>),
+    ),
+    security(("bearer_auth" = [])),
+    tag = "发现页"
+)]
+/// GET /api/v1/diary/discover
+///
+/// 获取发现页全部数据（每日推荐、热门话题、精选模板、达人日记）。
+/// 需要 `diary.journal.read` 权限。
+pub async fn get_discover<S>(
+    State(state): State<DiaryState>,
+    Extension(ctx): Extension<TenantContext>,
+) -> Result<Json<ApiResponse<DiscoverResp>>, AppError>
+where
+    DiaryState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    require_permission(&ctx, "diary.journal.read")?;
+
+    let resp = DiscoverService::get_discover(ctx.tenant_id, &state.db).await?;
+
+    Ok(Json(ApiResponse::ok(resp)))
+}

crates/erp-diary/src/handler/mod.rs

@@ -9,3 +9,4 @@ pub mod sticker_handler;
 pub mod achievement_handler;
 pub mod stats_handler;
 pub mod parent_handler;
+pub mod discover_handler;

crates/erp-diary/src/lib.rs

@@ -12,7 +12,7 @@ use erp_core::module::ErpModule;
 
 use crate::handler::{
     journal_handler, sync_handler, class_handler, topic_handler, comment_handler,
-    sticker_handler, achievement_handler, stats_handler, parent_handler,
+    sticker_handler, achievement_handler, stats_handler, parent_handler, discover_handler,
 };
 
 /// 暖记日记业务模块
@@ -268,5 +268,10 @@ impl DiaryModule {
                 "/diary/parent/bindings/{binding_id}/reject",
                 axum::routing::post(parent_handler::reject_binding),
             )
+            // 发现页 — 灵感、热门话题、精选模板、达人日记
+            .route(
+                "/diary/discover",
+                axum::routing::get(discover_handler::get_discover),
+            )
     }
 }

crates/erp-diary/src/service/discover_service.rs

@@ -0,0 +1,312 @@
+// 发现页服务 — 聚合热门话题、精选模板、每日推荐、达人日记
+
+use sea_orm::{
+    ColumnTrait, ConnectionTrait, DatabaseConnection, EntityTrait, QueryFilter, QueryOrder,
+    QuerySelect, Statement,
+};
+use uuid::Uuid;
+
+use crate::dto::{DiscoverResp, ExpertDiaryItem, InspirationItem, TagCount, TemplateResp};
+use crate::entity::template;
+use crate::error::DiaryResult;
+
+/// 发现页服务 — 聚合查询，一次返回全部板块数据
+pub struct DiscoverService;
+
+/// 心情 → emoji 映射
+fn mood_to_emoji(mood: &str) -> &'static str {
+    match mood {
+        "happy" => "😊",
+        "calm" => "😌",
+        "sad" => "😢",
+        "angry" => "😤",
+        "thinking" => "🤔",
+        _ => "📝",
+    }
+}
+
+impl DiscoverService {
+    /// 获取发现页全部数据（4 个板块并发查询）
+    pub async fn get_discover(
+        tenant_id: Uuid,
+        db: &DatabaseConnection,
+    ) -> DiaryResult<DiscoverResp> {
+        let (inspiration, topics, templates, experts) = tokio::join!(
+            Self::daily_inspiration(tenant_id, db),
+            Self::hot_topics(tenant_id, db),
+            Self::featured_templates(tenant_id, db),
+            Self::expert_diaries(tenant_id, db),
+        );
+
+        Ok(DiscoverResp {
+            daily_inspiration: inspiration?,
+            hot_topics: topics?,
+            featured_templates: templates?,
+            expert_diaries: experts?,
+        })
+    }
+
+    /// 每日推荐 — 基于日期种子的确定性随机，选取一篇共享日记
+    ///
+    /// 使用日期字符串作为盐，与 UUID 拼接后取哈希，得到每天固定但不同的结果。
+    /// 无共享日记时返回 None。
+    async fn daily_inspiration(
+        tenant_id: Uuid,
+        db: &DatabaseConnection,
+    ) -> DiaryResult<Option<InspirationItem>> {
+        let date_seed = chrono::Utc::now().format("%Y-%m-%d").to_string();
+
+        let sql = r#"
+            SELECT id, title, author_id, mood, date
+            FROM journal_entries
+            WHERE tenant_id = $1
+              AND is_private = false
+              AND shared_to_class = true
+              AND deleted_at IS NULL
+            ORDER BY (
+                ('x' || md5(id::text || $2))::bit(32)::int
+            ) DESC
+            LIMIT 1
+        "#;
+
+        let stmt = Statement::from_sql_and_values(
+            sea_orm::DatabaseBackend::Postgres,
+            sql,
+            [tenant_id.into(), date_seed.into()],
+        );
+
+        let rows = db.query_all(stmt).await?;
+
+        if let Some(row) = rows.into_iter().next() {
+            let journal_id: Uuid = row.try_get_by_index::<Uuid>(0)?;
+            let title: String = row.try_get_by_index::<String>(1)?;
+            let author_id: Uuid = row.try_get_by_index::<Uuid>(2)?;
+            let mood: String = row.try_get_by_index::<String>(3)?;
+            let date: chrono::NaiveDate = row.try_get_by_index::<chrono::NaiveDate>(4)?;
+
+            // Phase 1: 用 author_id 前 4 位作为昵称后缀
+            let author_hex = author_id.to_string().replace('-', "");
+            let suffix = &author_hex[..4];
+            let author_name = format!("小暖·{}", suffix);
+
+            Ok(Some(InspirationItem {
+                journal_id,
+                title,
+                author_name,
+                mood,
+                date,
+            }))
+        } else {
+            Ok(None)
+        }
+    }
+
+    /// 热门话题 — 统计所有非私密日记的标签频率，返回 TOP 8
+    async fn hot_topics(
+        tenant_id: Uuid,
+        db: &DatabaseConnection,
+    ) -> DiaryResult<Vec<TagCount>> {
+        let sql = r#"
+            SELECT tag, COUNT(*) AS count
+            FROM (
+                SELECT jsonb_array_elements_text(tags) AS tag
+                FROM journal_entries
+                WHERE tenant_id = $1
+                  AND is_private = false
+                  AND deleted_at IS NULL
+                  AND tags IS NOT NULL
+            ) sub
+            GROUP BY tag
+            ORDER BY count DESC
+            LIMIT 8
+        "#;
+
+        let stmt = Statement::from_sql_and_values(
+            sea_orm::DatabaseBackend::Postgres,
+            sql,
+            [tenant_id.into()],
+        );
+
+        let rows = db.query_all(stmt).await?;
+
+        let topics = rows
+            .into_iter()
+            .filter_map(|row| {
+                let tag: String = row.try_get_by_index::<String>(0).ok()?;
+                let count: i64 = row.try_get_by_index::<i64>(1).ok()?;
+                Some(TagCount { tag, count })
+            })
+            .collect();
+
+        Ok(topics)
+    }
+
+    /// 精选模板 — 官方模板，按名称排序，最多 6 个
+    async fn featured_templates(
+        tenant_id: Uuid,
+        db: &DatabaseConnection,
+    ) -> DiaryResult<Vec<TemplateResp>> {
+        let templates = template::Entity::find()
+            .filter(template::Column::TenantId.eq(tenant_id))
+            .filter(template::Column::IsOfficial.eq(true))
+            .filter(template::Column::DeletedAt.is_null())
+            .order_by_asc(template::Column::Name)
+            .limit(6)
+            .all(db)
+            .await?;
+
+        Ok(templates
+            .into_iter()
+            .map(|t| TemplateResp {
+                id: t.id,
+                name: t.name,
+                description: None,
+                preview_url: t.thumbnail_url,
+                template_data: None, // 发现页不需要完整布局数据
+                category: t.category,
+                is_free: true,
+            })
+            .collect())
+    }
+
+    /// 达人日记 — 不同作者最近共享的日记，以评论数作为热度代理
+    async fn expert_diaries(
+        tenant_id: Uuid,
+        db: &DatabaseConnection,
+    ) -> DiaryResult<Vec<ExpertDiaryItem>> {
+        let sql = r#"
+            SELECT
+                j.id, j.title, j.author_id, j.mood,
+                j.created_at,
+                COUNT(c.id) AS comment_count
+            FROM journal_entries j
+            LEFT JOIN comments c
+                ON c.journal_id = j.id
+                AND c.deleted_at IS NULL
+            WHERE j.tenant_id = $1
+              AND j.is_private = false
+              AND j.shared_to_class = true
+              AND j.deleted_at IS NULL
+            GROUP BY j.id
+            ORDER BY j.created_at DESC
+            LIMIT 20
+        "#;
+
+        let stmt = Statement::from_sql_and_values(
+            sea_orm::DatabaseBackend::Postgres,
+            sql,
+            [tenant_id.into()],
+        );
+
+        let rows = db.query_all(stmt).await?;
+
+        // 去重：每个作者只保留最新一篇，最多 5 位作者
+        let mut seen_authors = std::collections::HashSet::new();
+        let mut experts = Vec::new();
+
+        for row in rows {
+            let author_id: Uuid = row.try_get_by_index::<Uuid>(2)?;
+            if seen_authors.contains(&author_id) {
+                continue;
+            }
+            if experts.len() >= 5 {
+                break;
+            }
+            seen_authors.insert(author_id);
+
+            let journal_id: Uuid = row.try_get_by_index::<Uuid>(0)?;
+            let title: String = row.try_get_by_index::<String>(1)?;
+            let mood: String = row.try_get_by_index::<String>(3)?;
+            let created_at: chrono::DateTime<chrono::Utc> =
+                row.try_get_by_index::<chrono::DateTime<chrono::Utc>>(4)?;
+            let comment_count: i64 = row.try_get_by_index::<i64>(5)?;
+
+            let author_hex = author_id.to_string().replace('-', "");
+            let suffix = &author_hex[..4];
+            let author_name = format!("日记达人·{}", suffix);
+
+            experts.push(ExpertDiaryItem {
+                journal_id,
+                title,
+                author_id,
+                author_name,
+                author_emoji: mood_to_emoji(&mood).to_string(),
+                content_preview: String::new(), // Phase 1: 无 content_preview 列，暂留空
+                like_count: comment_count,
+                created_at,
+            });
+        }
+
+        Ok(experts)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn mood_to_emoji_maps_correctly() {
+        assert_eq!(mood_to_emoji("happy"), "😊");
+        assert_eq!(mood_to_emoji("calm"), "😌");
+        assert_eq!(mood_to_emoji("sad"), "😢");
+        assert_eq!(mood_to_emoji("angry"), "😤");
+        assert_eq!(mood_to_emoji("thinking"), "🤔");
+        assert_eq!(mood_to_emoji("unknown"), "📝");
+    }
+
+    #[test]
+    fn discover_resp_structure() {
+        let resp = DiscoverResp {
+            daily_inspiration: Some(InspirationItem {
+                journal_id: Uuid::nil(),
+                title: "测试日记".into(),
+                author_name: "小暖·a3f2".into(),
+                mood: "happy".into(),
+                date: chrono::NaiveDate::from_ymd_opt(2026, 6, 7).unwrap(),
+            }),
+            hot_topics: vec![
+                TagCount {
+                    tag: "期末备考".into(),
+                    count: 42,
+                },
+            ],
+            featured_templates: vec![],
+            expert_diaries: vec![],
+        };
+        let json = serde_json::to_string(&resp).unwrap();
+        assert!(json.contains("\"daily_inspiration\""));
+        assert!(json.contains("\"hot_topics\""));
+        assert!(json.contains("\"期末备考\""));
+        assert!(json.contains("\"count\":42"));
+    }
+
+    #[test]
+    fn discover_resp_null_inspiration() {
+        let resp = DiscoverResp {
+            daily_inspiration: None,
+            hot_topics: vec![],
+            featured_templates: vec![],
+            expert_diaries: vec![],
+        };
+        let json = serde_json::to_string(&resp).unwrap();
+        assert!(json.contains("\"daily_inspiration\":null"));
+    }
+
+    #[test]
+    fn expert_diary_item_serializes() {
+        let item = ExpertDiaryItem {
+            journal_id: Uuid::nil(),
+            title: "春日漫步手账".into(),
+            author_id: Uuid::nil(),
+            author_name: "日记达人·abcd".into(),
+            author_emoji: "🌸".into(),
+            content_preview: "记录春天的每一朵花开...".into(),
+            like_count: 342,
+            created_at: chrono::Utc::now(),
+        };
+        let json = serde_json::to_string(&item).unwrap();
+        assert!(json.contains("\"like_count\":342"));
+        assert!(json.contains("\"author_emoji\":\"🌸\""));
+    }
+}

crates/erp-diary/src/service/mod.rs

@@ -11,3 +11,4 @@ pub mod achievement_service;
 pub mod mood_stats_service;
 pub mod content_safety_service;
 pub mod parent_service;
+pub mod discover_service;

crates/erp-server/src/main.rs

@@ -208,6 +208,7 @@ struct MessageApiDoc;
         erp_diary::handler::parent_handler::list_pending_bindings,
         erp_diary::handler::parent_handler::confirm_binding,
         erp_diary::handler::parent_handler::reject_binding,
+        erp_diary::handler::discover_handler::get_discover,
     ),
     components(schemas(
         erp_diary::dto::CreateJournalReq,
@@ -241,6 +242,10 @@ struct MessageApiDoc;
         erp_diary::handler::parent_handler::DeleteChildDataReq,
         erp_diary::handler::parent_handler::BindingResp,
         erp_diary::handler::parent_handler::DeleteResultResp,
+        erp_diary::dto::DiscoverResp,
+        erp_diary::dto::InspirationItem,
+        erp_diary::dto::TagCount,
+        erp_diary::dto::ExpertDiaryItem,
     ))
 )]
 struct DiaryApiDoc;