feat: Radio volume control - server-wide slider synced via SSE

- Server: inlineVolume on AudioResource, POST /api/radio/volume endpoint
- Volume persisted per guild, broadcast via SSE to all clients
- Frontend: volume slider in bottom bar with debounced API calls
- Volume icon changes based on level (muted/low/normal)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/plugins/radio/index.ts

@@ -24,8 +24,10 @@ interface GuildRadioState {
   startedAt: string;
   ffmpeg: ChildProcess;
   player: ReturnType<typeof createAudioPlayer>;
+  resource: ReturnType<typeof createAudioResource>;
   channelId: string;
   channelName: string;
+  volume: number;
 }
 
 interface Favorite {
@@ -39,6 +41,17 @@ interface Favorite {
 // ── State ──
 const guildRadioState = new Map<string, GuildRadioState>();
 
+function getVolume(guildId: string): number {
+  const vols = getState<Record<string, number>>('radio_volumes', {});
+  return vols[guildId] ?? 0.5;
+}
+
+function setVolume(guildId: string, vol: number): void {
+  const vols = getState<Record<string, number>>('radio_volumes', {});
+  vols[guildId] = vol;
+  setState('radio_volumes', vols);
+}
+
 function getFavorites(): Favorite[] {
   return getState<Favorite[]>('radio_favorites', []);
 }
@@ -118,10 +131,13 @@ async function startStream(
     }
   });
 
-  // AudioResource + Player
+  // AudioResource + Player (inlineVolume für Lautstärkeregelung)
+  const vol = getVolume(guildId);
   const resource = createAudioResource(ffmpeg.stdout!, {
     inputType: StreamType.Raw,
+    inlineVolume: true,
   });
+  resource.volume?.setVolume(vol);
 
   const player = createAudioPlayer();
   player.play(resource);
@@ -137,7 +153,8 @@ async function startStream(
   guildRadioState.set(guildId, {
     stationId, stationName, placeName, country,
     streamUrl, startedAt: new Date().toISOString(),
-    ffmpeg, player, channelId: voiceChannelId, channelName,
+    ffmpeg, player, resource, channelId: voiceChannelId, channelName,
+    volume: vol,
   });
 
   broadcastState(guildId);
@@ -151,6 +168,7 @@ function broadcastState(guildId: string): void {
     type: 'radio',
     plugin: 'radio',
     guildId,
+    volume: state?.volume ?? getVolume(guildId),
     playing: state ? {
       stationId: state.stationId,
       stationName: state.stationName,
@@ -252,6 +270,21 @@ const radioPlugin: Plugin = {
       res.json({ ok: true });
     });
 
+    // ── Volume ──
+    app.post('/api/radio/volume', (req, res) => {
+      const { guildId, volume } = req.body ?? {};
+      if (!guildId || volume == null) return res.status(400).json({ error: 'guildId, volume required' });
+      const vol = Math.max(0, Math.min(1, Number(volume)));
+      setVolume(guildId, vol);
+      const state = guildRadioState.get(guildId);
+      if (state) {
+        state.volume = vol;
+        state.resource.volume?.setVolume(vol);
+      }
+      sseBroadcast({ type: 'radio_volume', plugin: 'radio', guildId, volume: vol });
+      res.json({ ok: true, volume: vol });
+    });
+
     // ── Favoriten lesen ──
     app.get('/api/radio/favorites', (_req, res) => {
       res.json(getFavorites());
@@ -299,6 +332,7 @@ const radioPlugin: Plugin = {
 
   getSnapshot() {
     const playing: Record<string, any> = {};
+    const volumes: Record<string, number> = {};
     for (const [gId, st] of guildRadioState) {
       playing[gId] = {
         stationId: st.stationId,
@@ -308,10 +342,12 @@ const radioPlugin: Plugin = {
         startedAt: st.startedAt,
         channelName: st.channelName,
       };
+      volumes[gId] = st.volume;
     }
     return {
       radio: {
         playing,
+        volumes,
         favorites: getFavorites(),
         placesCount: getPlacesCount(),
       },