⚡ perf(playground): optimize config loading and saving to reduce console spam

- Cache initial config using useRef to prevent repeated loadConfig() calls
- Fix useEffect dependencies to only trigger on actual config changes
- Modify debouncedSaveConfig dependency from function reference to actual config values
- Update handleConfigReset to use DEFAULT_CONFIG directly instead of reloading
- Prevent excessive console logging during chat interactions and frequent re-renders

This resolves the issue where console was flooded with:
"配置已从本地存储加载" and "配置已保存到本地存储" messages,
especially during active chat sessions where logs appeared every second.

Fixes: Frequent config load/save operations causing performance issues

web/src/App.js

@@ -22,7 +22,7 @@ import { Layout } from '@douyinfe/semi-ui';
 import Midjourney from './pages/Midjourney';
 import Pricing from './pages/Pricing/index.js';
 import Task from './pages/Task/index.js';
-import Playground from './pages/Playground/Playground.js';
+import Playground from './pages/Playground/index.js';
 import OAuth2Callback from './components/OAuth2Callback.js';
 import PersonalSetting from './components/PersonalSetting.js';
 import Setup from './pages/Setup/index.js';