feat: use lifespans for more reliable setup/teardown

projects/fal/src/fal/app.py

@@ -3,6 +3,7 @@
 import inspect
 import os
 import fal.api
+from contextlib import asynccontextmanager
 from fal.toolkit import mainify
 from fastapi import FastAPI
 from typing import Any, NamedTuple, Callable, TypeVar, ClassVar
@@ -72,14 +73,21 @@ def serve(self) -> None:
         import uvicorn
 
         app = self._build_app()
-        self.setup()
         uvicorn.run(app, host="0.0.0.0", port=8080)
 
     def _build_app(self) -> FastAPI:
         from fastapi import FastAPI
         from fastapi.middleware.cors import CORSMiddleware
 
-        _app = FastAPI()
+        @asynccontextmanager
+        async def lifespan(app: FastAPI):
+            self.setup()
+            try:
+                yield
+            finally:
+                self.teardown()
+
+        _app = FastAPI(lifespan=lifespan)
 
         _app.add_middleware(
             CORSMiddleware,
@@ -145,6 +153,9 @@ def order_schema_object(schema: dict[str, Any]):
 
         return spec
 
+    def teardown(self):
+        """Teardown the application after serving."""
+
 
 @mainify
 def endpoint(path: str) -> Callable[[EndpointT], EndpointT]: