feat(scrobble): web statistics view (Phase 3 UI)

Opens from Settings ("Meine Statistiken") as a self-contained modal overlay
(no router changes). Fetches GET /scrobble/stats and renders: totals tiles
(plays + listening time), a per-bucket play series, top artists/tracks/albums
with mini bars, and a 24h listening clock. Period tabs (all / this year /
last 30 days) switch from/to + bucket. Vanilla inline SVG-free bars, no chart
lib. Reuses .modal-overlay.open + design tokens; sends local tz offset for
day bucketing. Graceful empty/error/unconfigured states. SW cache -> ns-v65.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'ns-v64';
+const CACHE = 'ns-v65';
 const PRECACHE = ['/', 'index.html', 'manifest.json', 'icon.svg'];
 const SKIP_PATHS = ['/rest/stream', '/rest/download', '/config.js'];
 // Auth token params stripped from cache keys so artwork survives across sessions/token refreshes.