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/handler/message_handler.rs

@@ -0,0 +1,122 @@
+use axum::extract::{Extension, Path, Query, State};
+use axum::extract::FromRef;
+use axum::Json;
+use uuid::Uuid;
+
+use erp_core::error::AppError;
+use erp_core::rbac::require_permission;
+use erp_core::types::{ApiResponse, PaginatedResponse, TenantContext};
+use validator::Validate;
+
+use crate::dto::{MessageQuery, MessageResp, SendMessageReq, UnreadCountResp};
+use crate::message_state::MessageState;
+use crate::service::message_service::MessageService;
+
+/// 查询消息列表。
+pub async fn list_messages<S>(
+    State(_state): State<MessageState>,
+    Extension(ctx): Extension<TenantContext>,
+    Query(query): Query<MessageQuery>,
+) -> Result<Json<ApiResponse<PaginatedResponse<MessageResp>>>, AppError>
+where
+    MessageState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    require_permission(&ctx, "message:list")?;
+
+    let db = &_state.db;
+    let page = query.page.unwrap_or(1);
+    let page_size = query.page_size.unwrap_or(20);
+
+    let (messages, total) = MessageService::list(ctx.tenant_id, ctx.user_id, &query, db).await?;
+
+    let total_pages = (total + page_size - 1) / page_size;
+    Ok(Json(ApiResponse::ok(PaginatedResponse {
+        data: messages,
+        total,
+        page,
+        page_size,
+        total_pages,
+    })))
+}
+
+/// 获取未读消息数量。
+pub async fn unread_count<S>(
+    State(_state): State<MessageState>,
+    Extension(ctx): Extension<TenantContext>,
+) -> Result<Json<ApiResponse<UnreadCountResp>>, AppError>
+where
+    MessageState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    let result = MessageService::unread_count(ctx.tenant_id, ctx.user_id, &_state.db).await?;
+    Ok(Json(ApiResponse::ok(result)))
+}
+
+/// 发送消息。
+pub async fn send_message<S>(
+    State(_state): State<MessageState>,
+    Extension(ctx): Extension<TenantContext>,
+    Json(req): Json<SendMessageReq>,
+) -> Result<Json<ApiResponse<MessageResp>>, AppError>
+where
+    MessageState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    require_permission(&ctx, "message:send")?;
+
+    req.validate()
+        .map_err(|e| AppError::Validation(e.to_string()))?;
+
+    let resp = MessageService::send(
+        ctx.tenant_id,
+        ctx.user_id,
+        &req,
+        &_state.db,
+        &_state.event_bus,
+    )
+    .await?;
+
+    Ok(Json(ApiResponse::ok(resp)))
+}
+
+/// 标记消息已读。
+pub async fn mark_read<S>(
+    State(_state): State<MessageState>,
+    Extension(ctx): Extension<TenantContext>,
+    Path(id): Path<Uuid>,
+) -> Result<Json<ApiResponse<()>>, AppError>
+where
+    MessageState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    MessageService::mark_read(id, ctx.tenant_id, ctx.user_id, &_state.db).await?;
+    Ok(Json(ApiResponse::ok(())))
+}
+
+/// 标记所有消息已读。
+pub async fn mark_all_read<S>(
+    State(_state): State<MessageState>,
+    Extension(ctx): Extension<TenantContext>,
+) -> Result<Json<ApiResponse<()>>, AppError>
+where
+    MessageState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    MessageService::mark_all_read(ctx.tenant_id, ctx.user_id, &_state.db).await?;
+    Ok(Json(ApiResponse::ok(())))
+}
+
+/// 删除消息。
+pub async fn delete_message<S>(
+    State(_state): State<MessageState>,
+    Extension(ctx): Extension<TenantContext>,
+    Path(id): Path<Uuid>,
+) -> Result<Json<ApiResponse<()>>, AppError>
+where
+    MessageState: FromRef<S>,
+    S: Clone + Send + Sync + 'static,
+{
+    MessageService::delete(id, ctx.tenant_id, ctx.user_id, &_state.db).await?;
+    Ok(Json(ApiResponse::ok(())))
+}