feat: v1.29.0 — Radio fast-start, seek fix, OGG, error toasts, contributors

Incorporates PRs #38 (nisarg-78), #42 #43 #44 (JulianNymark) with fixes:

Audio / Playback
- Artist Radio starts immediately from fast getTopSongs (local library);
  getSimilarSongs2 (Last.fm) enriches queue in background — no more wait
- Fix seek audio glitch: EqualPowerFadeIn only resets to zero-gain on
  seeks to track start (<100 ms); all other seeks resume at unity gain
- OGG/Vorbis container support via symphonia-format-ogg (PR #42)
- Human-readable audio error messages in SizedDecoder (PR #44)
- Audio playback errors shown as themed toast notifications (PR #43)

Queue / Radio
- Infinite Queue: proactive load of 5 tracks (was 25) when ≤2 remain
- Radio: proactive reload at ≤2 remaining tracks, independent of
  Infinite Queue setting — radio no longer stops at last track
- Fix: clicking Start Radio multiple times no longer stacks duplicates
- Fix: Start Radio on artist keeps current song playing
- Manual tracks always appear before Radio, Radio before Auto-added
- Queue separators: "— Radio —" and "— Auto —" dividers
- Fix: radio proactive load now works even when songs lack artistId
  (uses currentRadioArtistId module var as fallback)

UI / UX
- Click synced lyrics lines to seek (PR #38)
- Volume scroll wheel on volume slider (PR #38)
- Lyrics: active / completed / upcoming visual states (PR #38)
- Shared toast utility (src/utils/toast.ts) replaces inline toast fn
- Auto-updater: relaunch_after_update Rust command exits first to
  release single-instance lock before spawning new process

About / Credits
- nisarg-78 and JulianNymark added to contributors (since v1.29.0)
- netherguy4 added as Special Thanks for feature ideas and feedback
- i18n: aboutSpecialThanksLabel in all 5 languages

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

src/utils/toast.ts

@@ -0,0 +1,87 @@
+/**
+ * Lightweight DOM-based toast notification.
+ * Uses the app's CSS custom properties so it respects the active theme.
+ * Multiple toasts stack vertically above each other.
+ */
+
+const TOAST_GAP = 8;
+const TOAST_BOTTOM_ANCHOR = 100;
+
+function getActiveToasts(): HTMLElement[] {
+  return Array.from(document.querySelectorAll<HTMLElement>('.psysonic-toast'));
+}
+
+function reflow(): void {
+  const toasts = getActiveToasts();
+  let bottom = TOAST_BOTTOM_ANCHOR;
+  for (let i = toasts.length - 1; i >= 0; i--) {
+    toasts[i].style.bottom = `${bottom}px`;
+    bottom += toasts[i].offsetHeight + TOAST_GAP;
+  }
+}
+
+export type ToastVariant = 'error' | 'info';
+
+export function showToast(text: string, durationMs = 4000, variant: ToastVariant = 'info'): void {
+  const isError = variant === 'error';
+
+  const toast = document.createElement('div');
+  toast.className = 'psysonic-toast';
+
+  const icon = document.createElement('span');
+  icon.textContent = isError ? '✕' : 'ℹ';
+  icon.style.cssText = `
+    flex-shrink: 0;
+    font-size: 11px;
+    font-weight: 700;
+    width: 18px;
+    height: 18px;
+    border-radius: 50%;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    background: ${isError ? 'var(--danger)' : 'var(--accent)'};
+    color: var(--bg-app);
+    line-height: 1;
+  `;
+
+  const msg = document.createElement('span');
+  msg.textContent = text;
+  msg.style.cssText = `flex: 1; min-width: 0;`;
+
+  toast.style.cssText = `
+    position: fixed;
+    bottom: ${TOAST_BOTTOM_ANCHOR}px;
+    left: 50%;
+    transform: translateX(-50%);
+    display: flex;
+    align-items: center;
+    gap: 10px;
+    background: var(--bg-card);
+    color: var(--text-primary);
+    border: 1px solid ${isError ? 'var(--danger)' : 'var(--border)'};
+    border-left: 3px solid ${isError ? 'var(--danger)' : 'var(--accent)'};
+    padding: 10px 16px;
+    border-radius: 8px;
+    font-size: 13.5px;
+    font-weight: 500;
+    z-index: 999999;
+    pointer-events: none;
+    box-shadow: 0 4px 24px rgba(0,0,0,0.45)${isError ? ', 0 0 0 1px color-mix(in srgb, var(--danger) 20%, transparent)' : ''};
+    white-space: normal;
+    word-break: break-word;
+    transition: bottom 150ms ease;
+    max-width: 480px;
+    width: max-content;
+  `;
+
+  toast.appendChild(icon);
+  toast.appendChild(msg);
+  document.body.appendChild(toast);
+  reflow();
+
+  setTimeout(() => {
+    toast.remove();
+    reflow();
+  }, durationMs);
+}