feat(theme): update wavesurfer colors to teal scheme

waveColor: subtle teal tint, progressColor/cursorColor match accent.

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

web/src/services/audioService.ts

@@ -69,9 +69,9 @@ class AudioService {
       // Fresh audio element per song. Lives on document.body so playback
       // continues even when the SongPage container is removed from the DOM.
       media: this.mediaElement,
-      waveColor: "rgba(255,255,255,0.09)",
-      progressColor: "#c8861a",
-      cursorColor: "#e8a22a",
+      waveColor: "rgba(20,184,166,0.18)",
+      progressColor: "#14b8a6",
+      cursorColor: "#2dd4bf",
       barWidth: 2,
       barRadius: 2,
       height: 104,