refactor(auth): E.45 — extract seven settings factories (#610)

Seven small domain-eng factories peel ~53 trivial setters out of the
authStore body:

- `createCacheStorageActions` — disk caches (max cache MB, download
  folder, offline download dir, hot-cache enable/MB/debounce/dir).
- `createDiscordSettingsActions` — rich presence, cover source,
  Bandsintown toggle, three template strings.
- `createUiAppearanceActions` — visual chrome: tray, titlebar, sidebar
  toggles, fullscreen-lyrics rendering, changelog banner, seekbar
  style, queue collapse, kinetic scroll, mini-player preload.
- `createLyricsSettingsActions` — lyrics fetch pipeline (server-first,
  netease enablement, source order, mode, static-only).
- `createTrackPreviewActions` — preview enable + per-location +
  start ratio (clamped 0…0.9) + duration (clamped 5…120s).
- `createDiscoveryActions` — mix min-rating filters (clamped 0…3),
  random-mix size (snapped to allowed bucket), lucky-mix visibility,
  random-nav mode, infinite-queue, preserve-play-next-order.
- `createPlumbingSettingsActions` — logging mode, getNowPlaying
  toggle, preload mode + custom seconds, audiobook exclusion,
  genre blacklist.

Pure code-move. authStore.ts: 428 → 384 LOC (−44).

src/store/authUiAppearanceActions.ts

@@ -0,0 +1,49 @@
+import type { AuthState } from './authStoreTypes';
+
+type SetState = (
+  partial: Partial<AuthState> | ((state: AuthState) => Partial<AuthState>),
+) => void;
+
+/**
+ * Visual / chrome settings. Pure pass-through setters: tray, titlebar,
+ * sidebar toggles, fullscreen lyrics rendering options, changelog
+ * banner. No side effects.
+ */
+export function createUiAppearanceActions(set: SetState): Pick<
+  AuthState,
+  | 'setShowArtistImages'
+  | 'setShowTrayIcon'
+  | 'setMinimizeToTray'
+  | 'setShowOrbitTrigger'
+  | 'setUseCustomTitlebar'
+  | 'setPreloadMiniPlayer'
+  | 'setLinuxWebkitKineticScroll'
+  | 'setSeekbarStyle'
+  | 'setQueueNowPlayingCollapsed'
+  | 'setShowFullscreenLyrics'
+  | 'setFsLyricsStyle'
+  | 'setSidebarLyricsStyle'
+  | 'setShowFsArtistPortrait'
+  | 'setFsPortraitDim'
+  | 'setShowChangelogOnUpdate'
+  | 'setLastSeenChangelogVersion'
+> {
+  return {
+    setShowArtistImages: (v) => set({ showArtistImages: v }),
+    setShowTrayIcon: (v) => set({ showTrayIcon: v }),
+    setMinimizeToTray: (v) => set({ minimizeToTray: v }),
+    setShowOrbitTrigger: (v) => set({ showOrbitTrigger: v }),
+    setUseCustomTitlebar: (v) => set({ useCustomTitlebar: v }),
+    setPreloadMiniPlayer: (v) => set({ preloadMiniPlayer: v }),
+    setLinuxWebkitKineticScroll: (v) => set({ linuxWebkitKineticScroll: v }),
+    setSeekbarStyle: (v) => set({ seekbarStyle: v }),
+    setQueueNowPlayingCollapsed: (v) => set({ queueNowPlayingCollapsed: v }),
+    setShowFullscreenLyrics: (v) => set({ showFullscreenLyrics: v }),
+    setFsLyricsStyle: (v) => set({ fsLyricsStyle: v }),
+    setSidebarLyricsStyle: (v) => set({ sidebarLyricsStyle: v }),
+    setShowFsArtistPortrait: (v) => set({ showFsArtistPortrait: v }),
+    setFsPortraitDim: (v) => set({ fsPortraitDim: v }),
+    setShowChangelogOnUpdate: (v) => set({ showChangelogOnUpdate: v }),
+    setLastSeenChangelogVersion: (v) => set({ lastSeenChangelogVersion: v }),
+  };
+}