Add camera functionality to voice demo with UI updates and state management

- Introduced a camera drawer for capturing images during the conversation flow.
- Added prompts for various camera states to guide users through the photo capture process.
- Updated HTML structure to include camera-related elements and integrated them with existing chat functionality.
- Enhanced JavaScript logic to manage camera state and button enabling/disabling based on connection status.
- Updated CSS for styling the camera drawer and its components, ensuring responsive design across devices.
- Adjusted README to reflect the new demo URL for voice functionality.

static/voice-demo/README.md

@@ -51,7 +51,7 @@ examples/webpage/
 2. Open the demo page served by the same process:
 
    ```text
-   http://127.0.0.1:8000/demo/
+   http://127.0.0.1:8000/voice-demo/
    ```
 
    The default websocket URL is derived from the page host
@@ -63,7 +63,7 @@ examples/webpage/
    ```json
    "server": {
      "serve_webpage": true,
-     "webpage_mount": "/demo"
+     "webpage_mount": "/voice-demo"
    }
    ```