feat: implement AI model API proxy service

backend/app/main.py

@@ -0,0 +1,46 @@
+"""FastAPI application entry point."""
+from contextlib import asynccontextmanager
+from fastapi import FastAPI
+
+from .database import init_db, seed_default_providers
+from .services.logger import async_logger
+from .routes import health_router, chat_router, openai_router, anthropic_router
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """Application lifespan handler."""
+    # Startup
+    await init_db()
+    await seed_default_providers()
+    await async_logger.start()
+
+    yield
+
+    # Shutdown
+    await async_logger.stop()
+
+
+app = FastAPI(
+    title="zzrouter",
+    description="AI Model API Proxy Service",
+    version="0.1.0",
+    lifespan=lifespan
+)
+
+# Register routers
+app.include_router(health_router)
+app.include_router(chat_router)
+app.include_router(openai_router)
+app.include_router(anthropic_router)
+
+
+def run_server():
+    """Run the server (entry point for script)."""
+    import uvicorn
+    from .config import HOST, PORT
+    uvicorn.run(app, host=HOST, port=PORT)
+
+
+if __name__ == "__main__":
+    run_server()