fix: v1.25.1 — Opus playback, single-instance enforcement

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

src/api/subsonic.ts

@@ -325,7 +325,7 @@ export async function reportNowPlaying(id: string): Promise<void> {
 }
 
 // ─── Stream URL ───────────────────────────────────────────────
-export function buildStreamUrl(id: string): string {
+export function buildStreamUrl(id: string, suffix?: string): string {
   const { getBaseUrl, getActiveServer } = useAuthStore.getState();
   const server = getActiveServer();
   const baseUrl = getBaseUrl();
@@ -336,6 +336,11 @@ export function buildStreamUrl(id: string): string {
     u: server?.username ?? '',
     t: token, s: salt, v: '1.16.1', c: 'psysonic', f: 'json',
   });
+  
+  if (suffix === 'opus') {
+    p.set('format', 'flac'); // Transcode OPUS to FLAC since Rust/Symphonia has no Opus decoder
+  }
+  
   return `${baseUrl}/rest/stream.view?${p.toString()}`;
 }