Files like Finder, richer mini player, in-app Back/Forward, Audio tab renamed Audiobooks

- Files: multi-select, batch move/copy/delete, rename checks, sort, filter, shortcuts, drag in (files and folders) to upload with progress and retries, drag to move, drag a file out to download
- Mini player: previous, seek bar with buffered range, time, shuffle/repeat, buffering spinner, swipe for next/previous, close
- Back/Forward bar that knows what history is possible
- Audio tab is now Audiobooks

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

users.js

@@ -13,7 +13,7 @@ fs.mkdirSync(DATA_DIR, { recursive: true });
 // Tabs an admin can switch on or off for a person. Home and Settings are always available to everyone (Settings only shows their own).
 const TABS = ['files', 'office', 'music', 'audio', 'podcast', 'verse', 'mail', 'calendar', 'tasks', 'search'];
 const ALWAYS = ['home', 'settings'];
-const TAB_LABELS = { files: 'Files', office: 'Office', music: 'Music', audio: 'Audio', podcast: 'Podcast', verse: 'Podcast Admin', mail: 'Mail', calendar: 'Calendar', tasks: 'Tasks', search: 'Search' };
+const TAB_LABELS = { files: 'Files', office: 'Office', music: 'Music', audio: 'Audiobooks', podcast: 'Podcast', verse: 'Podcast Admin', mail: 'Mail', calendar: 'Calendar', tasks: 'Tasks', search: 'Search' };
 
 let cache = null;
 const load = () => { if (cache) return cache; try { cache = JSON.parse(fs.readFileSync(USERS_FILE, 'utf8')); } catch { cache = { users: [] }; } if (!Array.isArray(cache.users)) cache.users = []; return cache; };