Add master display UI with audio output management and styling

- Implement main.js for the master display functionality, including WebSocket connection, audio output management, and state handling.
- Create style.css for the master display's visual design, ensuring a cohesive look and feel with a dark theme and responsive layout.
- Integrate device management with a fallback for non-Electron environments, allowing users to select audio outputs.
- Add features for managing favorites, including toggling favorites and filtering by genre.
- Enhance user experience with a responsive favorites grid and drag-to-scroll functionality.

server/routes/rooms.js

@@ -0,0 +1,61 @@
+// /api/rooms — list/create rooms, manage members, fetch state.
+
+import { Router } from 'express';
+import { requireUser } from '../auth.js';
+import {
+    listRoomsForUser, getRoomBySlug, createRoom,
+    addMember, removeMember, listMembers, isMember, getRoomState,
+    ensurePersonalRoom
+} from '../rooms.js';
+import { getStation } from '../stations.js';
+
+export const router = Router();
+router.use(requireUser);
+
+router.get('/', (req, res) => {
+    // Guarantee a personal room exists for every authenticated user.
+    ensurePersonalRoom(req.user);
+    res.json(listRoomsForUser(req.user.id));
+});
+
+router.post('/', (req, res) => {
+    const { name, slug } = req.body || {};
+    if (!name || typeof name !== 'string') return res.status(400).json({ error: 'name required' });
+    const room = createRoom({ name: name.trim(), slug: slug?.trim() || undefined, ownerId: req.user.id });
+    res.status(201).json(room);
+});
+
+router.get('/:slug', (req, res) => {
+    const room = getRoomBySlug(req.params.slug);
+    if (!room) return res.status(404).json({ error: 'not found' });
+    if (!isMember(room.id, req.user.id)) return res.status(403).json({ error: 'not a member' });
+    const state = getRoomState(room.id);
+    const station = state.station_id ? getStation(state.station_id) : null;
+    res.json({ ...room, state: { ...state, station } });
+});
+
+router.get('/:slug/members', (req, res) => {
+    const room = getRoomBySlug(req.params.slug);
+    if (!room) return res.status(404).json({ error: 'not found' });
+    if (!isMember(room.id, req.user.id)) return res.status(403).json({ error: 'not a member' });
+    res.json(listMembers(room.id));
+});
+
+router.post('/:slug/members', (req, res) => {
+    const room = getRoomBySlug(req.params.slug);
+    if (!room) return res.status(404).json({ error: 'not found' });
+    if (!isMember(room.id, req.user.id)) return res.status(403).json({ error: 'not a member' });
+    const userId = Number(req.body?.user_id);
+    if (!userId) return res.status(400).json({ error: 'user_id required' });
+    const role = req.body?.role === 'guest' ? 'guest' : 'member';
+    addMember(room.id, userId, role);
+    res.json(listMembers(room.id));
+});
+
+router.delete('/:slug/members/:userId', (req, res) => {
+    const room = getRoomBySlug(req.params.slug);
+    if (!room) return res.status(404).json({ error: 'not found' });
+    if (!isMember(room.id, req.user.id)) return res.status(403).json({ error: 'not a member' });
+    removeMember(room.id, Number(req.params.userId));
+    res.json(listMembers(room.id));
+});