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`.

services/discord-gateway/src/modules/command-handler/voice.handler.ts

@@ -111,6 +111,67 @@ export class VoiceHandler {
     }
   }
 
+  async handleGuildsList(cmd: CommandMessage): Promise<CommandReply<unknown>> {
+    if (!this.client) {
+      return {
+        id: cmd.id,
+        success: false,
+        data: null,
+        error: "Gateway not initialized",
+      };
+    }
+
+    try {
+      const guilds = this.client.guilds.cache
+        .map((guild) => ({ id: guild.id, name: guild.name }))
+        .sort((a, b) => a.name.localeCompare(b.name));
+      return { id: cmd.id, success: true, data: guilds };
+    } catch (err) {
+      const msg = err instanceof Error ? err.message : String(err);
+      return { id: cmd.id, success: false, data: null, error: msg };
+    }
+  }
+
+  async handleWatchableChannels(
+    cmd: CommandMessage,
+  ): Promise<CommandReply<unknown>> {
+    if (!this.client) {
+      return {
+        id: cmd.id,
+        success: false,
+        data: null,
+        error: "Gateway not initialized",
+      };
+    }
+
+    const guildId = String(cmd.payload.guildId ?? "");
+    if (!guildId) {
+      return {
+        id: cmd.id,
+        success: false,
+        data: null,
+        error: "guildId is required",
+      };
+    }
+
+    try {
+      const guild = await this.client.guilds.fetch(guildId);
+      const channels = await guild.channels.fetch();
+      const textChannels = channels
+        .filter((c) => c?.type === "GUILD_TEXT")
+        .map((c) => ({
+          id: c.id,
+          name: c.name,
+          type: c.type,
+        }));
+
+      return { id: cmd.id, success: true, data: textChannels };
+    } catch (err) {
+      const msg = err instanceof Error ? err.message : String(err);
+      return { id: cmd.id, success: false, data: null, error: msg };
+    }
+  }
+
   async handleVoiceTransmitStart(
     cmd: CommandMessage,
   ): Promise<CommandReply<unknown>> {