feat(ai): 新增 AI 客服聊天功能 + 消息页重构为小华助手

- 新增 POST /ai/chat 端点，由 LLM（Ollama qwen3）担任 24h 健康客服"小华"
- 新增 ai.chat.send 权限，绑定管理员/患者/医生/护士/健康管理师角色
- 消息页从咨询列表重构为单窗口 AI 对话（欢迎态 + 聊天态 + 快捷问诊）
- 通知功能迁移到"我的"页面菜单项（带未读角标），独立通知列表页
- 修复气泡文字截断：改用百分比 max-width + block Text + pre-wrap 换行
- 修复权限绑定：迁移 SQL 角色名从英文改为中文（admin→管理员，patient→患者）

crates/erp-ai/src/handler/chat_handler.rs

@@ -0,0 +1,138 @@
+use axum::Json;
+use axum::extract::{Extension, FromRef, State};
+use erp_core::rbac::require_permission;
+use erp_core::types::{ApiResponse, TenantContext};
+use serde::{Deserialize, Serialize};
+
+use crate::dto::GenerateRequest;
+use crate::state::AiState;
+
+// === 请求 / 响应 ===
+
+#[derive(Debug, Deserialize, utoipa::ToSchema)]
+pub struct ChatRequest {
+    pub message: String,
+    pub history: Option<Vec<ChatHistoryItem>>,
+}
+
+#[derive(Debug, Deserialize, Serialize, utoipa::ToSchema)]
+pub struct ChatHistoryItem {
+    pub role: String,
+    pub content: String,
+}
+
+#[derive(Debug, Serialize, utoipa::ToSchema)]
+pub struct ChatResponse {
+    pub reply: String,
+    pub message_id: String,
+}
+
+const SYSTEM_PROMPT: &str = r#"你是 HMS 健康管理平台的 AI 客服助手"小华"。你的职责是：
+1. 回答用户的健康咨询问题
+2. 帮助用户了解体检报告指标
+3. 提供预约挂号、用药提醒等服务指导
+4. 推荐健康生活方式
+
+注意：
+- 你不能替代医生的诊断，遇到需要诊断的问题请建议用户就医
+- 不能推荐具体药物，只能提供一般性健康建议
+- 语气要亲切、专业、耐心
+- 回复要简洁明了，避免过长
+- 如果用户问的问题超出健康范围，礼貌引导回到健康话题"#;
+
+#[utoipa::path(
+    post,
+    path = "/ai/chat",
+    request_body = ChatRequest,
+    responses((status = 200, description = "AI 客服回复")),
+    tag = "AI 客服",
+    security(("bearer_auth" = [])),
+)]
+pub async fn chat<S>(
+    Extension(ctx): Extension<TenantContext>,
+    State(state): State<S>,
+    Json(body): Json<ChatRequest>,
+) -> Result<Json<ApiResponse<ChatResponse>>, erp_core::error::AppError>
+where
+    AiState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    require_permission(&ctx, "ai.chat.send")?;
+
+    let message = body.message.trim();
+    if message.is_empty() {
+        return Err(erp_core::error::AppError::Validation("消息不能为空".into()));
+    }
+    if message.len() > 2000 {
+        return Err(erp_core::error::AppError::Validation(
+            "消息长度不能超过 2000 字".into(),
+        ));
+    }
+
+    let user_prompt = match body.history {
+        Some(ref hist) if !hist.is_empty() => {
+            let filtered: Vec<&ChatHistoryItem> = hist
+                .iter()
+                .filter(|h| h.role == "user" || h.role == "assistant")
+                .collect();
+            let start = filtered.len().saturating_sub(10);
+            let ctx: String = filtered[start..]
+                .iter()
+                .map(|h| {
+                    format!(
+                        "{}: {}",
+                        if h.role == "user" { "用户" } else { "助手" },
+                        h.content
+                    )
+                })
+                .collect::<Vec<_>>()
+                .join("\n");
+            format!("历史对话:\n{}\n\n用户最新消息: {}", ctx, message)
+        }
+        _ => message.to_string(),
+    };
+
+    let ai_state = AiState::from_ref(&state);
+    let resolved = ai_state
+        .provider_registry
+        .resolve("auto")
+        .await
+        .map_err(|e| {
+            tracing::error!(error = %e, "AI provider resolve failed");
+            erp_core::error::AppError::Internal("AI 服务暂时不可用，请稍后再试".into())
+        })?;
+
+    let req = GenerateRequest {
+        system_prompt: SYSTEM_PROMPT.to_string(),
+        user_prompt,
+        model: String::new(),
+        temperature: 0.7,
+        max_tokens: 1024,
+    };
+
+    tracing::info!(
+        tenant_id = %ctx.tenant_id,
+        user_id = %ctx.user_id,
+        msg_len = message.len(),
+        "AI chat request"
+    );
+
+    let resp = resolved.provider().generate(req).await.map_err(|e| {
+        tracing::error!(error = %e, "AI chat generate failed");
+        erp_core::error::AppError::Internal("AI 服务暂时不可用，请稍后再试".into())
+    })?;
+
+    let message_id = uuid::Uuid::now_v7().to_string();
+
+    tracing::info!(
+        tenant_id = %ctx.tenant_id,
+        message_id = %message_id,
+        tokens = resp.output_tokens,
+        "AI chat response sent"
+    );
+
+    Ok(Json(ApiResponse::ok(ChatResponse {
+        reply: resp.content,
+        message_id,
+    })))
+}