feat(backend): Phase 0 项目骨架完成 — 后端/前端/数据库/Docker

- 后端：FastAPI + SQLAlchemy + Alembic，7 张核心表迁移成功
- 前端：Next.js 16 + TailwindCSS 4 + 三端布局（投资人/创始人/Admin）
- 数据库：PostgreSQL 16，7 张核心实体表（tenants/users/companies/monthly_reports/health_scores/risk_events/audit_logs）
- Docker：docker-compose.yml + 前后端 Dockerfile
- 测试：健康检查 4 个测试全部 GREEN
- 文档：README/run.md/AGENTS.md/docs 体系完整

backend/app/main.py

@@ -0,0 +1,65 @@
+"""FastAPI 应用入口。
+
+注册中间件、路由、异常处理。
+"""
+
+import uuid
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI, Request
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
+
+from app.schemas.common import error
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """应用生命周期管理。"""
+    # startup
+    yield
+    # shutdown
+
+
+app = FastAPI(
+    title="AIPortPilot",
+    description="AI+ Portfolio Operating System — 投后管理与组合协同平台",
+    version="0.1.0",
+    lifespan=lifespan,
+)
+
+# CORS
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["http://localhost:3000"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+@app.middleware("http")
+async def trace_id_middleware(request: Request, call_next):
+    """为每个请求注入 trace_id。"""
+    trace_id = request.headers.get("X-Trace-Id", str(uuid.uuid4()))
+    request.state.trace_id = trace_id
+    response = await call_next(request)
+    response.headers["X-Trace-Id"] = trace_id
+    return response
+
+
+@app.exception_handler(Exception)
+async def global_exception_handler(request: Request, exc: Exception):
+    """全局异常处理。"""
+    trace_id = getattr(request.state, "trace_id", str(uuid.uuid4()))
+    return JSONResponse(
+        status_code=500,
+        content=error(code=-1, message="内部服务器错误"),
+        headers={"X-Trace-Id": trace_id},
+    )
+
+
+@app.get("/health")
+async def health_check():
+    """健康检查端点。"""
+    return {"status": "ok", "service": "aiportpilot-backend", "version": "0.1.0"}