Show reference-data update time, location filter UI, and tile fixes

- Status gains reference_updated_at (sourced from reference.db's file
  mtime, so it needs no separate persisted state) and the sidebar's
  "Your library" panel shows it as a relative "Updated Xh ago" stamp
  that self-refreshes every minute.
- Add a Location field to the Library tab's filters panel, wired to the
  new LibraryFilter.location.
- Bump every font-size in the stylesheet up one step for a slightly
  larger, easier-to-read UI overall.
- Fix the library/deck tile view's +/- quantity overlay permanently
  covering the card art's own printed mana cost (top-right corner) —
  it now only fades in on hover/focus, like the other row actions.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/App.tsx

@@ -72,6 +72,21 @@ const NAV: { id: Tab; label: string; icon: ReactNode }[] = [
   },
 ];
 
+/** Compact relative time, e.g. "2h ago" — for the "database updated" stamp. */
+function formatRelativeTime(epochSeconds: number): string {
+  const diffSec = Math.round((Date.now() - epochSeconds * 1000) / 1000);
+  if (diffSec < 30) return "just now";
+  const mins = Math.round(diffSec / 60);
+  if (mins < 60) return `${mins}m ago`;
+  const hours = Math.round(mins / 60);
+  if (hours < 24) return `${hours}h ago`;
+  const days = Math.round(hours / 24);
+  if (days < 30) return `${days}d ago`;
+  const months = Math.round(days / 30);
+  if (months < 12) return `${months}mo ago`;
+  return `${Math.round(months / 12)}y ago`;
+}
+
 /** Percent-fill (0..100) of one segment, given overall cumulative percent. */
 function segmentFill(stages: IngestStageInfo[], index: number, overallPercent: number): number {
   let start = 0;
@@ -107,6 +122,14 @@ export default function App() {
     };
   }, [refreshStatus]);
 
+  // Force a re-render every minute so the "Updated Xh ago" stamp stays fresh
+  // over a long session without needing an actual status refetch.
+  const [, tick] = useState(0);
+  useEffect(() => {
+    const interval = setInterval(() => tick((n) => n + 1), 60000);
+    return () => clearInterval(interval);
+  }, []);
+
   const ready = status?.reference_ready ?? false;
 
   // Keep the sidebar's library summary fresh: fetch once card data is ready,
@@ -279,7 +302,12 @@ export default function App() {
                   </>
                 )}
                 <div className="lib-stats-sub">
-                  {status?.card_count.toLocaleString()} cards in database
+                  <div>{status?.card_count.toLocaleString()} cards in database</div>
+                  {status?.reference_updated_at != null && (
+                    <div title={new Date(status.reference_updated_at * 1000).toLocaleString()}>
+                      Updated {formatRelativeTime(status.reference_updated_at)}
+                    </div>
+                  )}
                 </div>
               </div>
             )}