feat: add SFX volume control and improve audio feedback

- Implemented separate sound effects volume control in settings.
- Updated backend to handle new `sfx_volume` parameter.
- Enhanced UI to include sound effects volume slider in admin panel.
- Integrated sound effects for various user interactions (clicks, navigation, alerts).
- Added a new global sound engine to manage audio synthesis without external files.
- Updated documentation for Docker deployment and Windows packaging.
- Refactored audio context management to ensure sound effects are available post user interaction.

backend/templates/admin.html

@@ -230,10 +230,15 @@
             <input type="number" id="imageDuration" value="{{ image_duration }}" min="1" max="300">
           </div>
           <div class="form-group">
-            <label>音量</label>
+            <label>音量（媒体）</label>
             <input type="range" id="volumeRange" min="0" max="100" value="{{ volume }}">
             <div class="volume-label" id="volumeLabel">{{ volume }}%</div>
           </div>
+          <div class="form-group">
+            <label>音量（音效）</label>
+            <input type="range" id="sfxVolumeRange" min="0" max="100" value="{{ sfx_volume }}">
+            <div class="volume-label" id="sfxVolumeLabel">{{ sfx_volume }}%</div>
+          </div>
         </div>
       </div>