feat(perf): 3-state animation mode (Full / Reduced / Static) (#441)

* feat(perf): 3-state animation mode (Full / Reduced / Static)

Replaces the boolean `reducedAnimations` toggle with a three-way
`animationMode` setting, suggested by Viktor Petrovich after the
Windows audio fix (PR #426) shipped and confirmed a measurable
GPU drop:

- `full` (default): native frame rate, marquee scrolls normally
- `reduced`: 30 fps cap on the animated seekbar wave; player
  marquee runs at half speed
- `static`: rAF loop disabled; the seekbar repaints from the
  ~2 Hz audio:progress heartbeat. Player title/artist truncate
  with ellipsis instead of scrolling.

Migration in `onRehydrateStorage` maps legacy
`reducedAnimations: true` to `'reduced'`, anything else to
`'full'`. Static is opt-in only.

Settings UI follows the ReplayGain Auto/Track/Album pattern with
a contextual hint that explains what each mode does.

i18n: 5 new keys across 8 locales, 2 legacy keys removed.

* docs(changelog): add #441 3-state animation mode entry

* chore(credits): add #441 to Psychotoxical contributions

src/styles/layout.css

@@ -1516,12 +1516,23 @@ html[data-platform="windows"] .player-bar.floating {
   width: 100%;
 }
 
+/* `static` animation mode: never scroll, truncate with ellipsis instead. */
+.marquee-wrap[data-anim-mode="static"] {
+  text-overflow: ellipsis;
+}
+
 .marquee-scroll {
   display: inline-block;
   animation: player-marquee 12s linear infinite;
   animation-delay: 2s;
 }
 
+/* `reduced` animation mode: double the marquee cycle so visual change
+   per second is roughly halved. */
+.marquee-wrap[data-anim-mode="reduced"] .marquee-scroll {
+  animation-duration: 24s;
+}
+
 @keyframes player-marquee {
   0%,   12% { transform: translateX(0); }
   78%,  88% { transform: translateX(var(--marquee-amount)); }