feat(now-playing): draggable widget cards with per-user layout (#267)

Each dashboard card (Album, Top Songs, Credits, Artist, Discography,
On Tour) is now a widget the user grabs and drops anywhere — reorder
within a column or move across columns. Layout persists per-install
via the new nowPlayingLayoutStore (Zustand + localStorage, same shape
as sidebarStore with an onRehydrateStorage guard for unknown IDs).

Drag uses psyDnD (useDragSource / psy-drop event, the mouse-event
based system from DragDropContext) — HTML5 native DnD is a no-go on
WebKitGTK Linux where it always shows a forbidden cursor. The whole
card is the drag handle; the column listens via a document-level
mousemove for the drop indicator and via a global psy-drop listener
that reads the latest hovered column from a ref, so drops below the
last card still land correctly regardless of column height.

Visibility is toggled from a layout menu in the top-right of the
dashboard — two sections (visible / hidden) plus a reset-to-defaults
button. No hide buttons on the cards themselves (keeps the card UI
uncluttered). An equal-height grid (align-items: stretch + min-height
on columns) keeps the drop zone active for the full vertical span of
either column.

Co-authored-by: Psychotoxical <dev@psysonic.app>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/locales/de.ts

@@ -117,6 +117,13 @@ export const deTranslation = {
     rgAutoTooltip: 'ReplayGain (Auto)',
     showMoreTracks: '{{count}} weitere anzeigen',
     showLessTracks: 'Weniger anzeigen',
+    hideCard: 'Karte ausblenden',
+    layoutMenu: 'Layout',
+    visibleCards: 'Sichtbare Karten',
+    hiddenCards: 'Ausgeblendete Karten',
+    noHiddenCards: 'Keine ausgeblendeten Karten',
+    resetLayout: 'Layout zurücksetzen',
+    emptyColumn: 'Karten hier ablegen',
   },
   contextMenu: {
     playNow: 'Direkt abspielen',