feat(audio): bit-perfect hi-res playback + underrun hardening (opt-in alpha)

Safe mode (default): all audio outputs at 44.1 kHz, rodio resamples
internally. Maximum stability out of the box.

Hi-Res mode (alpha toggle): stream opens at the file's native sample rate
(e.g. 88.2/96/192 kHz) for bit-perfect output.

Rust (audio.rs):
- open_stream_for_rate(): CPAL queries device supported configs, finds
  exact rate match or falls back to highest available / device default.
- create_engine() thread: ThreadPriority::Max (silently ignored without
  CAP_SYS_NICE), loop handles rate-switch requests, PIPEWIRE_LATENCY
  scales with rate (8192 frames for >48 kHz ≈ 93 ms quantum), keeps
  PULSE_LATENCY_MSEC in sync.
- audio_play(): hi_res_enabled param gates effective_rate (44100 vs
  native); stream re-opens only when needed; 150 ms PipeWire settle +
  500 ms sink pre-fill (pause→append→sleep→play) for hi-res tracks.
- audio_chain_preload(): hi_res_enabled param; rate-mismatch bail skipped
  in safe mode so gapless chains always work at 44.1 kHz.
- SizedDecoder MSS buffer: 4 MB (was 512 KB) to reduce Symphonia read
  overhead on high-bitrate hi-res files.
- thread-priority crate added to Cargo.toml.

Frontend:
- authStore: enableHiRes (bool, default false) + setEnableHiRes.
- playerStore: hiResEnabled passed to all audio_play /
  audio_chain_preload invoke calls.
- Settings → Audio tab: "Native Hi-Res Playback" toggle with Alpha
  badge and stability warning, i18n for all 7 languages.

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

src/locales/nb.ts

@@ -431,6 +431,9 @@ export const nbTranslation = {
     hotCacheDebounceImmediate: 'Umiddelbart',
     hotCacheDebounceSeconds: '{{n}} sek',
     hotCacheClearBtn: 'Tøm varm buffer',
+    hiResTitle: 'Innebygd hi-res-avspilling',
+    hiResEnabled: 'Aktiver innebygd hi-res-avspilling',
+    hiResDesc: "Begrenser utdata til 44,1 kHz som standard for maksimal stabilitet. Aktiver kun hvis maskinvare og nettverk støtter høye samplingsrater (88,2 kHz+) pålitelig.",
     showArtistImages: 'Vis artistbilder',
     showArtistImagesDesc: 'Last inn og vis artistbilder i artistoversikten. Denne er deaktivert som standard, for å redusere disk-I/O og nettverksbelastningen på store biblioteker.',
     minimizeToTray: 'Minimer til oppgavelinjen',