refactor(voice): optimize recording pipeline and improve performance

Refactor the voice recording and playback systems to improve efficiency, reduce latency, and enhance Docker build performance.

- **Infrastructure**: Optimize Dockerfiles using build mounts for pnpm cache and reorder layers for better caching of dependencies and build tools.
- **Backend/Gateway**:
  - Refactor `broadcast` module to use a generic event-based system instead of hardcoded functions.
  - Simplify voice recording logic by merging metadata and segment management into a unified `segment.ts`.
  - Optimize audio downsampling in `streamSetup.ts` using `Int16Array` views for better performance.
  - Implement `withFallback` utility for more robust Redis/Database command execution.
- **Frontend**:
  - Optimize audio playback visualization using pre-computed level shapes and efficient RMS calculation.
  - Reduce latency in voice commands by prioritizing WebSocket communication over HTTP.
  - Improve base64 encoding efficiency in audio transmission.
- **General**:
  - Add default value for `ADMIN_PASSWORD` in shared config.
  - Fix Docker healthcheck to use `127.0.0.1` instead of `localhost`.

infra/docker/docker-compose.yml

@@ -80,8 +80,10 @@ services:
     image: ghcr.io/${OWNER:-mytheclipse}/bete-frontend:latest
     container_name: imphenbot-frontend
     restart: unless-stopped
+    # Use 127.0.0.1 instead of localhost — Alpine's BusyBox wget tries IPv6 first
+    # for 'localhost' which fails since nginx only listens on IPv4
     healthcheck:
-      test: ["CMD", "wget", "-qO-", "http://localhost:3000/"]
+      test: ["CMD", "wget", "-qO-", "http://127.0.0.1:3000/"]
       interval: 30s
       timeout: 5s
       start_period: 5s