feat: 接入 Fish Audio TTS 引擎

- 新增 fish_audio_service.py，使用 REST API 调用
- voice_id: 34e841f0f4ff44aca6e396debf2776d4（蓝皓音色克隆）
- 支持语速/音量控制，情绪通过内嵌标签实现
- 前端引擎下拉菜单新增 Fish Audio 选项

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/app.js

@@ -22,6 +22,11 @@ const ENGINE_CONFIG = {
         name: '豆包',
         emotionMode: 'global',
         color: '#7c5cfc'
+    },
+    fish_audio: {
+        name: 'Fish Audio',
+        emotionMode: 'global',
+        color: '#f59e0b'
     }
 };
 

frontend/index.html

@@ -41,6 +41,7 @@
                             <option value="minimax">MiniMax</option>
                             <option value="cosyvoice">CosyVoice</option>
                             <option value="doubao">豆包</option>
+                            <option value="fish_audio">Fish Audio</option>
                         </select>
                         <span class="toolbar-divider"></span>
                         <span class="toolbar-label">情绪：</span>