feat(media): default music volume 30% instead of 100%

Volume play music terlalu besar buat user — default sekarang 0.3 (30%)
di semua layer: player gateway (musicVolume=0.3), backend state/schema
(default 0.3), dan UI slider (fallback 0.3). User tetap bisa naikin
manual via slider volume di dashboard.

services/backend/src/modules/media/media.schema.ts

@@ -6,7 +6,7 @@ export const mediaQueueSchema = z.object({
 });
 
 export const mediaVolumeSchema = z.object({
-  volume: z.number().min(0).max(1).default(1.0),
+  volume: z.number().min(0).max(1).default(0.3),
 });
 
 export type MediaQueueInput = z.infer<typeof mediaQueueSchema>;

services/backend/src/modules/media/media.service.ts

@@ -44,7 +44,7 @@ const DEFAULT_COMMAND_TIMEOUT_MS = 5000;
 const DEFAULT_STATE: MediaState = {
   playing: false,
   activeMode: null,
-  musicVolume: 1.0,
+  musicVolume: 0.3,
   current: null,
   queue: [],
 };
@@ -65,7 +65,7 @@ function normalizeMediaState(raw: Record<string, unknown>): MediaState {
   return {
     playing,
     activeMode,
-    musicVolume: Number(raw.musicVolume ?? 1.0),
+    musicVolume: Number(raw.musicVolume ?? 0.3),
     current: (raw.current as MediaItem | null) ?? null,
     queue: (raw.queue as MediaItem[]) ?? [],
   };

services/discord-gateway/src/modules/voice-recording/player.ts

@@ -18,7 +18,7 @@ export class DiscordPlayer {
   private connection: VoiceConnection | null = null;
   private owner: DiscordPlayerOwner = "none";
   private resource: AudioResource | null = null;
-  private musicVolume = 1;
+  private musicVolume = 0.3;
   private idleCallback: (() => void) | null = null;
   /** Set before manual stop() calls to distinguish from natural track end. */
   private manualStop = false;

services/frontend/src/components/media/music-player.tsx

@@ -147,8 +147,8 @@ export function MusicPlayer({ ws, initialData }: MusicPlayerProps) {
             <Volume2 className="size-4 text-muted-foreground" />
             <Slider
               className="w-24"
-              defaultValue={[mediaState?.musicVolume ?? 0.5]}
-              value={[mediaState?.musicVolume ?? 0.5]}
+              defaultValue={[mediaState?.musicVolume ?? 0.3]}
+              value={[mediaState?.musicVolume ?? 0.3]}
               onValueChange={handleVolume}
               min={0}
               max={1}

services/frontend/src/lib/hooks/use-media-player.tsx

@@ -41,7 +41,7 @@ export function MediaPlayerProvider({ children }: { children: ReactNode }) {
   const ws = useWebSocket();
   const [state, setState] = useState<MediaState>({
     playing: false,
-    musicVolume: 0.5,
+    musicVolume: 0.3,
     current: null,
     queue: [],
   });