feat(ui): themed startup splash with deferred window show (#1030)

* feat(ui): add themed startup splash with deferred window show

Show a theme-aware loading splash before the Vite bundle mounts, hide the
native window until it paints, and use per-theme logo gradient colors.

* docs: note startup splash in CHANGELOG and credits for PR #1030

* docs: attribute PR #1030 startup splash to cucadmuh

src/config/settingsCredits.ts

@@ -154,6 +154,7 @@ const CONTRIBUTOR_ENTRIES = [
       'Audio: Symphonia 0.6 migration with libopus adapter 0.3; ranged-stream start latency fix (probe seek-gate) and a probe timeout so a stalled stream no longer hangs playback start (PR #999)',
       'Offline experience — unified media layout (cache/library/favorites), localPlaybackStore, library-index Offline Library, favorites auto-sync, cached album/playlist/artist pin reconcile, mixed-server offline queue, and single mediaDir setting (PR #1008)',
       'Offline browse — local-bytes catalog when server is down, integration contract (context/policy/resolvers), disconnect nav fork, Home stale-cache feed, read-only context menus, PlayerBar rating/favorite guard (PR #1017)',
+      'Themed startup splash before Vite loads — deferred window show, per-theme logo gradient (PR #1030)',
     ],
   },
   {