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>

src/main.js

@@ -3,6 +3,7 @@ import { toast } from './utils.js';
 import { api, fetchRomajiIndex, loadRomajiOverrides } from './api.js';
 import { injectPWA } from './pwa.js';
 import { initPlayLog } from './player/scrobbleLog.js';
+import { openStats, closeStats } from './ui/stats.js';
 import { loadSavedTheme } from './themes.js';
 import { initScrollRows } from './ui/components.js';
 import {
@@ -330,6 +331,7 @@ Object.assign(window, {
   // UI / Modals
   openSettings, closeSettings, saveSettings, confirmDisconnect, checkBackend,
   openSidebar, closeSidebar, switchNavMode, showCtxMenu,
+  openStats, closeStats,
   // Views
   loadAlbums, loadStarred, loadRandom, filterStarred, filterPlaylist,
   plReorderEnter, plReorderSave, plReorderCancel, toggleAllGenres,