Lobby: leagues are play buttons w/ arrow; remove background music feature

- OnlineLobbyScreen: each league row is now a tappable play button (queues a
  ranked match at that league's stake) with a forward arrow; the cheapest
  enterable league is highlighted gold. Drops the redundant separate "ranked
  random" CTA and the select-then-play step.
- Remove the background-music feature entirely: deleted the floating MusicToggle,
  the TopBar music button, and the Profile audio music toggle + style picker.
  sound.startMusic() is now an inert no-op so music never plays (sfx unchanged).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/sound.ts

@@ -210,43 +210,8 @@ class SoundManager {
     },
   };
 
-  startMusic() {
-    if (!this.musicEnabled || this.musicTimer || !this.ctx || !this.musicGain) return;
-    const playNote = () => {
-      if (!this.ctx || !this.musicGain) return;
-      const cfg = this.TRACKS[this.musicTrack];
-      const freq = cfg.notes[this.step % cfg.notes.length];
-      this.step++;
-      const osc = this.ctx.createOscillator();
-      const g = this.ctx.createGain();
-      const t = this.ctx.currentTime;
-      osc.type = cfg.type;
-      osc.frequency.value = freq;
-      g.gain.setValueAtTime(0.0001, t);
-      g.gain.exponentialRampToValueAtTime(cfg.peak, t + cfg.attack);
-      g.gain.exponentialRampToValueAtTime(0.0001, t + cfg.dur);
-      osc.connect(g);
-      g.connect(this.musicGain);
-      osc.start(t);
-      osc.stop(t + cfg.dur + 0.1);
-      // soft fifth harmony (santoor) every other note
-      if (cfg.fifth && this.step % 2 === 0) {
-        const o2 = this.ctx.createOscillator();
-        const g2 = this.ctx.createGain();
-        o2.type = "sine";
-        o2.frequency.value = freq * 1.5;
-        g2.gain.setValueAtTime(0.0001, t);
-        g2.gain.exponentialRampToValueAtTime(0.22, t + 0.3);
-        g2.gain.exponentialRampToValueAtTime(0.0001, t + 1.4);
-        o2.connect(g2);
-        g2.connect(this.musicGain);
-        o2.start(t);
-        o2.stop(t + 1.5);
-      }
-    };
-    playNote();
-    this.musicTimer = setInterval(playNote, this.TRACKS[this.musicTrack].gap);
-  }
+  /** Background music was removed from the game — these are inert no-ops. */
+  startMusic() {}
 
   stopMusic() {
     if (this.musicTimer) {