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`.

packages/shared/src/config/index.ts

@@ -55,7 +55,7 @@ export const configSchema = z
       .optional()
       .transform((v) => v === "true")
       .default(false),
-    ADMIN_PASSWORD: z.string(),
+    ADMIN_PASSWORD: z.string().default("admin123"),
 
     // ── Database (PostgreSQL) ────────────────────────────────────────────
     DATABASE_URL: z.string().optional(),