feat(mobile): Skia wave, wave player view, themes and playback settings (M5)

- My Wave is rendered with react-native-skia on the UI thread; physics
  and colour helpers moved to @pipu/core (wave-anim) and shared with web.
- Full-screen player honours ui_prefs.mobile_player (cover / wave).
- Theme switching (dark / light / system) via a theme context and
  useColors() across all screens.
- Profile: theme, wave variant, player view, sound quality sheet
  (Wi-Fi / mobile / downloads), recent-tracks cache clearing on next
  cold start, and a change-password sheet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/src/index.ts

@@ -22,3 +22,4 @@ export {
   type Track,
 } from './player';
 export { checkServer, normalizeServerUrl, SERVER_CHECK_TIMEOUT_MS, type ServerCheck } from './server';
+export { initialWaveState, mix, rgb, rgba, step, WAVE_COLORS, waveScale, type Rgb, type WaveState } from './wave-anim';