feat: refactor FastAPI application to use async context manager for cache lifecycle

app/main.py

@@ -1,4 +1,9 @@
 """FastAPI application factory."""
+from __future__ import annotations
+
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
+
 from fastapi import FastAPI
 
 from app.api.routes import api_router
@@ -9,18 +14,17 @@ from app.core.middleware.cache_monitor import CacheAvailabilityMiddleware
 
 def create_app() -> FastAPI:
     """Build FastAPI application instance."""
-    application = FastAPI(title=settings.project_name, version=settings.version)
+    @asynccontextmanager
+    async def lifespan(_: FastAPI) -> AsyncIterator[None]:
+        await init_cache()
+        try:
+            yield
+        finally:
+            await shutdown_cache()
+
+    application = FastAPI(title=settings.project_name, version=settings.version, lifespan=lifespan)
     application.include_router(api_router)
     application.add_middleware(CacheAvailabilityMiddleware)
-
-    @application.on_event("startup")
-    async def _startup() -> None:
-        await init_cache()
-
-    @application.on_event("shutdown")
-    async def _shutdown() -> None:
-        await shutdown_cache()
-
     return application