feat(stats): shareable Top-Albums card export (#425)

* feat(stats): add shareable Top-Albums card export

Adds a shareable PNG export of the user's most-played albums,
available from the Statistics page under the "Most Played Albums"
section header.

Layout:
* 3 formats — Story (1080×1920, 9:16), Square (1080×1080), Twitter
  Card (1200×675, 16:9). Story and Square stack a centered URL footer;
  Twitter packs logo + label + URL into a single header row.
* 3 grid sizes — 3×3 (default), 4×4, 5×5. Modal fetches up to 25
  frequent albums on open so larger grids work even when the entry
  surface only loaded a handful.
* Cover tiles render the rank + play count in a thin black info strip
  at the bottom of the cover (rank left, "N Plays" right).
* Header label is hardcoded English ("Top Albums") so a shared image
  remains legible to followers who don't share the user's UI language.
  Caller can override via `opts.meta`.

Source path is local-only — `getAlbumList(type='frequent')` from
Subsonic. Last.fm is intentionally not used.

Implementation:
* `src/utils/exportAlbumCard.ts` — pure Canvas-API renderer. Reads
  theme accent / bg from the document's CSS variables so the export
  matches the active theme. Cover art is loaded through the existing
  `getCachedBlob` IndexedDB cache, so repeated exports are cheap.
  Wordmark is rendered from the `PsysonicLogo` React component via
  `renderToStaticMarkup`, with both gradient stops baked to a single
  accent color for crisp single-tone branding.
* `src/components/StatsExportModal.tsx` — UI: format + grid pickers,
  live downscaled preview, native save dialog via
  `@tauri-apps/plugin-dialog` + `plugin-fs`.
* `src/components/AlbumRow.tsx` — adds optional `headerExtra` slot so
  the share button sits next to the existing scroll-nav arrows.
* i18n keys added under `statistics.*` (`en`, `de`) — other locales
  fall back to English.

* docs(changelog): add Top-Albums card export for PR #425

src/locales/de.ts

@@ -1179,6 +1179,24 @@ export const deTranslation = {
     topRatedArtists: 'Bestbewertete Künstler',
     noRatedSongs: 'Noch keine bewerteten Songs. Songs in Album- oder Playlist-Ansicht bewerten.',
     noRatedArtists: 'Noch keine bewerteten Künstler.',
+    exportShare: 'Teilen',
+    exportTitle: 'Top-Alben teilen',
+    exportSubtitle: 'Ein teilbares Bild deiner meistgespielten Alben erstellen.',
+    exportFormat: 'Format',
+    exportFormatStory: 'Story',
+    exportFormatSquare: 'Quadrat',
+    exportFormatTwitter: 'Twitter-Card',
+    exportGrid: 'Raster',
+    exportGridLabel: '{{n}}×{{n}}',
+    exportPreview: 'Vorschau',
+    exportGenerate: 'Erstellen',
+    exportSave: 'Bild speichern…',
+    exportCancel: 'Abbrechen',
+    exportFooterLabel: 'Top-Alben',
+    exportNotEnough: 'Für ein {{n}}×{{n}}-Raster braucht es mindestens {{count}} Alben in der Library.',
+    exportSaving: 'Speichere…',
+    exportSaved: 'Gespeichert.',
+    exportSaveFailed: 'Bild konnte nicht gespeichert werden.',
   },
   player: {
     regionLabel: 'Musikplayer',