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>

backend/app/schemas/brief.py

@@ -20,6 +20,7 @@ class BriefCreateRequest(BaseModel):
     max_duration: Optional[int] = None
     other_requirements: Optional[str] = None
     attachments: Optional[List[dict]] = None
+    agency_attachments: Optional[List[dict]] = None
 
 
 class BriefUpdateRequest(BaseModel):
@@ -34,6 +35,12 @@ class BriefUpdateRequest(BaseModel):
     max_duration: Optional[int] = None
     other_requirements: Optional[str] = None
     attachments: Optional[List[dict]] = None
+    agency_attachments: Optional[List[dict]] = None
+
+
+class AgencyBriefUpdateRequest(BaseModel):
+    """代理商更新 Brief 请求（仅允许更新 agency_attachments）"""
+    agency_attachments: Optional[List[dict]] = None
 
 
 # ===== 响应 =====
@@ -53,6 +60,7 @@ class BriefResponse(BaseModel):
     max_duration: Optional[int] = None
     other_requirements: Optional[str] = None
     attachments: Optional[List[dict]] = None
+    agency_attachments: Optional[List[dict]] = None
     created_at: datetime
     updated_at: datetime
 

backend/app/schemas/project.py

@@ -12,6 +12,7 @@ class ProjectCreateRequest(BaseModel):
     """创建项目请求（品牌方操作）"""
     name: str = Field(..., min_length=1, max_length=255)
     description: Optional[str] = None
+    platform: Optional[str] = None
     start_date: Optional[datetime] = None
     deadline: Optional[datetime] = None
     agency_ids: Optional[List[str]] = None  # 分配的代理商 ID 列表
@@ -21,6 +22,7 @@ class ProjectUpdateRequest(BaseModel):
     """更新项目请求"""
     name: Optional[str] = Field(None, min_length=1, max_length=255)
     description: Optional[str] = None
+    platform: Optional[str] = None
     start_date: Optional[datetime] = None
     deadline: Optional[datetime] = None
     status: Optional[str] = Field(None, pattern="^(active|completed|archived)$")
@@ -45,6 +47,7 @@ class ProjectResponse(BaseModel):
     id: str
     name: str
     description: Optional[str] = None
+    platform: Optional[str] = None
     brand_id: str
     brand_name: Optional[str] = None
     status: str