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/dto.rs

@@ -75,7 +75,7 @@ fn default_priority() -> String {
 }
 
 /// 消息列表查询参数
-#[derive(Debug, Deserialize, ToSchema)]
+#[derive(Debug, Deserialize, ToSchema, utoipa::IntoParams)]
 pub struct MessageQuery {
     pub page: Option<u64>,
     pub page_size: Option<u64>,