fix: stopping background task properly on shutdown

router.py

@@ -4123,6 +4123,16 @@ async def startup_event() -> None:
 @app.on_event("shutdown")
 async def shutdown_event() -> None:
     await close_all_sse_queues()
+
+    # Stop background tasks first so they stop touching the DB before we close it.
+    for t in (token_worker_task, flush_task):
+        if t is not None:
+            t.cancel()
+            try:
+                await t
+            except (asyncio.CancelledError, Exception):
+                pass
+
     await flush_remaining_buffers()
     await app_state["session"].close()
 
@@ -4142,7 +4152,11 @@ async def shutdown_event() -> None:
         except Exception as e:
             print(f"[shutdown] Error closing httpx client {ep}: {e}")
 
-    if token_worker_task is not None:
-        token_worker_task.cancel()
-    if flush_task is not None:
-        flush_task.cancel()
+    # Close the aiosqlite connection last — its worker thread is non-daemon
+    # and would otherwise keep the interpreter alive after lifespan completes.
+    if db is not None:
+        try:
+            await db.close()
+            print("[shutdown] Closed token DB connection.")
+        except Exception as e:
+            print(f"[shutdown] Error closing DB: {e}")