feat: T1.5 风险工作台 — 后端 CRUD + 前端风险列表

- 后端：risks 路由（列表/详情/创建/更新/删除）+ 状态流转
- 前端：风险工作台页（卡片列表、状态筛选、内联状态切换、删除）
- 测试：6 个风险 CRUD 测试（总计 43 tests passed）
- 前端构建 13 路由成功

backend/app/schemas/risk.py

@@ -0,0 +1,54 @@
+"""风险事件相关 Pydantic schema。"""
+
+from datetime import datetime
+from pydantic import BaseModel, Field
+
+
+class RiskEventCreate(BaseModel):
+    """创建风险事件。"""
+
+    company_id: str
+    type: str = Field(..., description="financial/operational/org/ai_specific")
+    severity: str = Field(default="medium", description="low/medium/high/critical")
+    title: str = Field(..., min_length=1, max_length=200)
+    description: str | None = None
+    suggested_action: str | None = None
+
+
+class RiskEventUpdate(BaseModel):
+    """更新风险事件。"""
+
+    status: str | None = Field(default=None, description="open/assigned/in_progress/resolved/closed")
+    severity: str | None = None
+    assigned_to: str | None = None
+    description: str | None = None
+    suggested_action: str | None = None
+
+
+class RiskEventResponse(BaseModel):
+    """风险事件响应。"""
+
+    id: str
+    company_id: str
+    type: str
+    severity: str
+    status: str
+    title: str
+    description: str | None = None
+    evidence_json: dict | None = None
+    suggested_action: str | None = None
+    assigned_to: str | None = None
+    due_at: datetime | None = None
+    identified_at: datetime
+    closed_at: datetime | None = None
+    created_at: datetime
+    updated_at: datetime
+
+
+class RiskEventListResponse(BaseModel):
+    """风险列表响应。"""
+
+    items: list[RiskEventResponse]
+    total: int
+    page: int
+    page_size: int