perf: optimize app startup and background lifecycles

tests/unit/image-workspace-store.test.ts

@@ -258,6 +258,7 @@ describe('AI design task event store', () => {
       chunkIndex: 1,
       delta: '鲸鱼的轮廓。',
     } satisfies DesignAssistantDeltaEvent);
+    await new Promise<void>((resolve) => setTimeout(resolve, 60));
 
     expect(useImageWorkspaceStore.getState().pendingTurn?.assistantText)
       .toBe('可以，先强化鲸鱼的轮廓。');