feat: Brief附件/项目平台/规则AI解析/消息中心修复 + 项目创建通知

- Brief 支持代理商附件上传 (迁移 007)
- 项目新增 platform 字段 (迁移 008)，前端创建/展示平台信息
- 修复 AI 规则解析：处理中文引号导致 JSON 解析失败的问题
- 修复消息中心崩溃：补全后端消息类型映射 + fallback 保护
- 项目创建时自动发送消息通知
- .gitignore 排除 backend/data/ 数据库文件

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

frontend/types/brief.ts

@@ -34,6 +34,7 @@ export interface BriefResponse {
   max_duration?: number | null
   other_requirements?: string | null
   attachments?: BriefAttachment[] | null
+  agency_attachments?: BriefAttachment[] | null
   created_at: string
   updated_at: string
 }
@@ -49,4 +50,5 @@ export interface BriefCreateRequest {
   max_duration?: number
   other_requirements?: string
   attachments?: BriefAttachment[]
+  agency_attachments?: BriefAttachment[]
 }

frontend/types/project.ts

@@ -13,6 +13,7 @@ export interface ProjectResponse {
   id: string
   name: string
   description?: string | null
+  platform?: string | null
   brand_id: string
   brand_name?: string | null
   status: string
@@ -34,6 +35,7 @@ export interface ProjectListResponse {
 export interface ProjectCreateRequest {
   name: string
   description?: string
+  platform?: string
   start_date?: string
   deadline?: string
   agency_ids?: string[]
@@ -42,6 +44,7 @@ export interface ProjectCreateRequest {
 export interface ProjectUpdateRequest {
   name?: string
   description?: string
+  platform?: string
   start_date?: string
   deadline?: string
   status?: 'active' | 'completed' | 'archived'