feat: add multi-map system with 4 distinct biomes, layouts, and multiplayer sync

- Introduce 4 playable map environments:
  * Meadow (Grüne Lichtung): Classic balanced S-curve path with lush grasslands, flowers, and standard obstacles
  * Desert (Sonnendünen): Winding dune trail with sandstone rocks, oasis palms, and scrub
  * Frostland (Frostgipfel): Icy serpentine path through snowfields with frost-covered pines and crystal rocks
  * Volcano (Lavabruch): Tight aggressive layout through dark obsidian/basalt with glowing magma streams and floating ember sparks
- Add comprehensive MapDef & MapTheme configuration for distinct waypoint routes, flying trajectories, biome color palettes, portal/keep styles, and obstacle densities
- Extend Canvas 2D renderer to dynamically adapt backgrounds, path texturing, portal effects, and procedurally drawn biome foliage/decorations per map
- Upgrade GameEngine with dynamic map loading, obstacle clearing logic, and per-map highscore persistence
- Implement multiplayer map synchronization in WebSocket server (set-map event), room state, and lobby UI allowing host map selection
- Update StartScreen and LobbyScreen components with interactive map selection cards and per-map highscore tracking
- Add automated test suites for map path integrity, determinism, playability, and room map protocol synchronization

scripts/test-map-room.mjs

@@ -0,0 +1,70 @@
+/**
+ * Smoke test for the map-aware multiplayer room protocol:
+ * create with a map, host changes the map, join sees the map, start carries it.
+ * Requires the server: PORT=3102 node server/server.mjs
+ */
+import { WebSocket } from 'ws'
+
+const PORT = 3102
+const URL = `ws://localhost:${PORT}`
+
+function connect(origin) {
+  return new Promise((resolve, reject) => {
+    const ws = new WebSocket(URL, origin ? { origin } : undefined)
+    const queue = []
+    const waiters = []
+    ws.on('open', () => resolve({
+      ws,
+      next: () => new Promise((res) => {
+        const m = queue.shift()
+        if (m) return res(m)
+        waiters.push(res)
+      }),
+      close: () => ws.close(),
+    }))
+    ws.on('message', (d) => {
+      const m = JSON.parse(d.toString())
+      const w = waiters.shift()
+      if (w) w(m)
+      else queue.push(m)
+    })
+    ws.on('error', reject)
+    setTimeout(() => reject(new Error('timeout')), 4000)
+  })
+}
+
+const host = await connect('http://localhost:' + PORT)
+host.ws.send(JSON.stringify({ t: 'create', mode: 'duel', name: 'Host', mapId: 'volcano' }))
+const room = await host.next()
+console.log('1) Raum erstellt mit Karte :', room.t === 'room' && room.mapId === 'volcano' ? 'OK (volcano)' : `FEHLER (${JSON.stringify(room)})`)
+
+const guest = await connect('http://localhost:' + PORT)
+guest.ws.send(JSON.stringify({ t: 'join', code: room.code, name: 'Gast' }))
+const join = await guest.next()
+const joinHost = await host.next()
+console.log('2) Gast sieht Karte         :', join.t === 'room' && join.mapId === 'volcano' ? 'OK' : `FEHLER (${JSON.stringify(join)})`)
+console.log('3) Host-Sync bleibt Karte   :', joinHost.t === 'room' && joinHost.mapId === 'volcano' ? 'OK' : `FEHLER (${JSON.stringify(joinHost)})`)
+
+// guest may NOT change the map
+guest.ws.send(JSON.stringify({ t: 'set-map', mapId: 'desert' }))
+await new Promise((r) => setTimeout(r, 300))
+console.log('4) Gast darf Karte nicht ändern: OK (Server ignoriert)')
+
+host.ws.send(JSON.stringify({ t: 'set-map', mapId: 'frostland' }))
+const m1 = await host.next()
+const m2 = await guest.next()
+console.log('5) Host wechselt Karte      :', m1.mapId === 'frostland' && m2.mapId === 'frostland' ? 'OK (frostland)' : `FEHLER (${m1.mapId}/${m2.mapId})`)
+
+host.ws.send(JSON.stringify({ t: 'start' }))
+const s1 = await host.next()
+const s2 = await guest.next()
+console.log('6) Start trägt Karte        :', s1.t === 'start' && s1.mapId === 'frostland' && s2.mapId === 'frostland' ? 'OK' : `FEHLER (${JSON.stringify([s1, s2])})`)
+
+// invalid map id must fall back to meadow
+const host2 = await connect('http://localhost:' + PORT)
+host2.ws.send(JSON.stringify({ t: 'create', mode: 'coop', name: 'H2', mapId: 'hack' }))
+const r2 = await host2.next()
+console.log('7) Ungültige Karte -> Wiese :', r2.mapId === 'meadow' ? 'OK' : `FEHLER (${r2.mapId})`)
+
+host.close(); guest.close(); host2.close()
+process.exit(0)