第一步

backend/app/main.py

@@ -0,0 +1,68 @@
+"""AI Knowledge Link — FastAPI 应用工厂。
+
+Phase 1 只包含：配置校验、日志、异常处理器、健康检查、lifespan 资源管理。
+后续 Phase 逐步挂载：auth、knowledge-bases、documents、public /k/ 路由。
+"""
+
+from contextlib import asynccontextmanager
+from pathlib import Path
+
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.api.health import router as health_router
+from app.core.config import get_settings
+from app.core.db import dispose_engine
+from app.core.errors import register_exception_handlers
+from app.core.logging import get_logger, setup_logging
+
+logger = get_logger(__name__)
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    settings = get_settings()
+    setup_logging()
+
+    # 确保 data 目录存在
+    data_dir = settings.storage_root_path
+    data_dir.mkdir(parents=True, exist_ok=True)
+    logger.info("Starting backend (env=%s, data=%s)", settings.environment, data_dir)
+
+    yield
+
+    dispose_engine()
+    logger.info("Backend shutdown complete")
+
+
+def create_app() -> FastAPI:
+    settings = get_settings()
+    app = FastAPI(
+        title="AI Knowledge Link",
+        version="0.1.0",
+        lifespan=lifespan,
+        docs_url="/api/docs" if not settings.is_production else None,
+        openapi_url="/api/openapi.json" if not settings.is_production else None,
+    )
+
+    # CORS（开发期允许 Vite dev server）
+    app.add_middleware(
+        CORSMiddleware,
+        allow_origins=[settings.frontend_origin],
+        allow_credentials=True,
+        allow_methods=["GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"],
+        allow_headers=["Content-Type", "X-Requested-With"],
+    )
+
+    register_exception_handlers(app)
+
+    # 路由挂载
+    app.include_router(health_router, prefix="/api", tags=["health"])
+    # Phase 3+: app.include_router(auth_router, prefix="/api/auth", tags=["auth"])
+    # Phase 4+: app.include_router(kb_router, prefix="/api/knowledge-bases", tags=["knowledge-bases"])
+    # Phase 10+: app.include_router(public_router, tags=["public"])
+
+    return app
+
+
+app = create_app()