Restore print statements in lifespan example

These serve as illustrative markers for users reading the example.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

examples/lifespan.py

@@ -8,8 +8,10 @@ import responder
 @asynccontextmanager
 async def lifespan(app):
     # Startup: initialize resources
+    print("Starting up...")
     yield
     # Shutdown: clean up resources
+    print("Shutting down...")
 
 
 api = responder.API(lifespan=lifespan)