feat(message): add message center module (Phase 5)

Implement the complete message center with:
- Database migrations for message_templates, messages, message_subscriptions tables
- erp-message crate with entities, DTOs, services, handlers
- Message CRUD, send, read/unread tracking, soft delete
- Template management with variable interpolation
- Subscription preferences with DND support
- Frontend: messages page, notification panel, unread count badge
- Server integration with module registration and routing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/erp-message/src/dto.rs

@@ -0,0 +1,144 @@
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+use uuid::Uuid;
+use utoipa::ToSchema;
+use validator::Validate;
+
+// ============ 消息 DTO ============
+
+/// 消息响应
+#[derive(Debug, Serialize, ToSchema)]
+pub struct MessageResp {
+    pub id: Uuid,
+    pub tenant_id: Uuid,
+    pub template_id: Option<Uuid>,
+    pub sender_id: Option<Uuid>,
+    pub sender_type: String,
+    pub recipient_id: Uuid,
+    pub recipient_type: String,
+    pub title: String,
+    pub body: String,
+    pub priority: String,
+    pub business_type: Option<String>,
+    pub business_id: Option<Uuid>,
+    pub is_read: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub read_at: Option<DateTime<Utc>>,
+    pub is_archived: bool,
+    pub status: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub sent_at: Option<DateTime<Utc>>,
+    pub created_at: DateTime<Utc>,
+    pub updated_at: DateTime<Utc>,
+}
+
+/// 发送消息请求
+#[derive(Debug, Deserialize, Validate, ToSchema)]
+pub struct SendMessageReq {
+    #[validate(length(min = 1, max = 200, message = "标题不能为空且不超过200字符"))]
+    pub title: String,
+    #[validate(length(min = 1, message = "内容不能为空"))]
+    pub body: String,
+    pub recipient_id: Uuid,
+    #[serde(default = "default_recipient_type")]
+    pub recipient_type: String,
+    #[serde(default = "default_priority")]
+    pub priority: String,
+    pub template_id: Option<Uuid>,
+    pub business_type: Option<String>,
+    pub business_id: Option<Uuid>,
+}
+
+fn default_recipient_type() -> String {
+    "user".to_string()
+}
+
+fn default_priority() -> String {
+    "normal".to_string()
+}
+
+/// 消息列表查询参数
+#[derive(Debug, Deserialize, ToSchema)]
+pub struct MessageQuery {
+    pub page: Option<u64>,
+    pub page_size: Option<u64>,
+    pub is_read: Option<bool>,
+    pub priority: Option<String>,
+    pub business_type: Option<String>,
+    pub status: Option<String>,
+}
+
+/// 未读消息计数响应
+#[derive(Debug, Serialize, ToSchema)]
+pub struct UnreadCountResp {
+    pub count: i64,
+}
+
+// ============ 消息模板 DTO ============
+
+/// 消息模板响应
+#[derive(Debug, Serialize, ToSchema)]
+pub struct MessageTemplateResp {
+    pub id: Uuid,
+    pub tenant_id: Uuid,
+    pub name: String,
+    pub code: String,
+    pub channel: String,
+    pub title_template: String,
+    pub body_template: String,
+    pub language: String,
+    pub created_at: DateTime<Utc>,
+    pub updated_at: DateTime<Utc>,
+}
+
+/// 创建消息模板请求
+#[derive(Debug, Deserialize, Validate, ToSchema)]
+pub struct CreateTemplateReq {
+    #[validate(length(min = 1, max = 100, message = "名称不能为空且不超过100字符"))]
+    pub name: String,
+    #[validate(length(min = 1, max = 50, message = "编码不能为空且不超过50字符"))]
+    pub code: String,
+    #[serde(default = "default_channel")]
+    pub channel: String,
+    #[validate(length(min = 1, max = 200, message = "标题模板不能为空"))]
+    pub title_template: String,
+    #[validate(length(min = 1, message = "内容模板不能为空"))]
+    pub body_template: String,
+    #[serde(default = "default_language")]
+    pub language: String,
+}
+
+fn default_channel() -> String {
+    "in_app".to_string()
+}
+
+fn default_language() -> String {
+    "zh-CN".to_string()
+}
+
+// ============ 消息订阅偏好 DTO ============
+
+/// 消息订阅偏好响应
+#[derive(Debug, Serialize, ToSchema)]
+pub struct MessageSubscriptionResp {
+    pub id: Uuid,
+    pub tenant_id: Uuid,
+    pub user_id: Uuid,
+    pub notification_types: Option<serde_json::Value>,
+    pub channel_preferences: Option<serde_json::Value>,
+    pub dnd_enabled: bool,
+    pub dnd_start: Option<String>,
+    pub dnd_end: Option<String>,
+    pub created_at: DateTime<Utc>,
+    pub updated_at: DateTime<Utc>,
+}
+
+/// 更新消息订阅偏好请求
+#[derive(Debug, Deserialize, ToSchema)]
+pub struct UpdateSubscriptionReq {
+    pub notification_types: Option<serde_json::Value>,
+    pub channel_preferences: Option<serde_json::Value>,
+    pub dnd_enabled: Option<bool>,
+    pub dnd_start: Option<String>,
+    pub dnd_end: Option<String>,
+}