feat: add utoipa path annotations to all API handlers and wire OpenAPI spec

- Add #[utoipa::path] annotations to all 70+ handler functions across
  auth, config, workflow, and message modules
- Add IntoParams/ToSchema derives to Pagination, PaginatedResponse, ApiResponse
  in erp-core, and MessageQuery/TemplateQuery in erp-message
- Collect all module paths into OpenAPI spec via AuthApiDoc, ConfigApiDoc,
  WorkflowApiDoc, MessageApiDoc structs in erp-server main.rs
- Update openapi_spec handler to merge all module specs
- The /docs/openapi.json endpoint now returns complete API documentation
  with all endpoints, request/response schemas, and security requirements

crates/erp-message/src/handler/subscription_handler.rs

@@ -9,6 +9,18 @@ use crate::dto::UpdateSubscriptionReq;
 use crate::message_state::MessageState;
 use crate::service::subscription_service::SubscriptionService;
 
+#[utoipa::path(
+    put,
+    path = "/api/v1/message-subscriptions",
+    request_body = UpdateSubscriptionReq,
+    responses(
+        (status = 200, description = "成功", body = ApiResponse<crate::dto::MessageSubscriptionResp>),
+        (status = 401, description = "未授权"),
+        (status = 403, description = "权限不足"),
+    ),
+    security(("bearer_auth" = [])),
+    tag = "消息订阅"
+)]
 /// 更新消息订阅偏好。
 pub async fn update_subscription<S>(
     State(_state): State<MessageState>,