refactor: port backend and frontend to TypeScript classes (bun + vite)

Backend (src/server, runs on Bun):
- GibbzHttpServer (health, /api/ice, /api/rooms, static, keepalive tuning)
- SignalingServer with Peer/Room/RoomRegistry classes and typed messages
- IceConfigProvider (env STUN/TURN + coturn HMAC ephemeral creds)
- StaticFileServer (dist/ with public/ fallback, traversal guard)
- Tracing (OpenTelemetry SDK), AppConfig; createApp() factory for tests

Frontend (src/client, built by Vite):
- VoiceApp orchestrator implementing VoiceAppContext
- WebRtcManager + PeerSession (perfect negotiation, pc rebuild, quality monitor)
- SignalingClient + ReconnectController, AudioManager, SpatialAudio,
  Microphone/ScreenShare controllers, ScreensUi/RosterUi/SpatialMap/
  SpeakingMonitor, Settings/Welcome dialogs, LayoutManager, MatrixChat

Tooling: bun scripts (dev/start/test/typecheck), vite.config.ts root
src/client with publicDir public/static, vitest-config for CI-less runs,
bun-based Dockerfile (oven/bun:1), Makefile + README updated, legacy
server.js/tracing.js/test.js/public js removed.

Verified locally: tsc --noEmit clean, vitest run 6/6 green, vite build ok,
server smoke-tested serving dist + signaling endpoints under Node. Local
bun binary segfaults (SIGILL) on this host, so 'bun test' itself was not
executable here; tests are vitest-API compatible which bun test maps.

vite.config.ts

@@ -0,0 +1,29 @@
+import { defineConfig } from 'vite';
+import { nodePolyfills } from 'vite-plugin-node-polyfills';
+import path from 'node:path';
+
+// The client lives in src/client (index.html is the Vite root); static PWA
+// assets stay in public/static and are served/copied verbatim from the root.
+export default defineConfig({
+  root: path.resolve(import.meta.dirname, 'src/client'),
+  publicDir: path.resolve(import.meta.dirname, 'public/static'),
+  plugins: [
+    nodePolyfills({
+      include: ['buffer', 'crypto', 'events', 'stream', 'util'],
+      globals: {
+        Buffer: true,
+        global: true,
+        process: true,
+      },
+    }),
+  ],
+  build: {
+    outDir: path.resolve(import.meta.dirname, 'dist'),
+    emptyOutDir: true,
+    target: 'esnext',
+    minify: 'esbuild',
+    rollupOptions: {
+      input: path.resolve(import.meta.dirname, 'src/client/index.html'),
+    },
+  },
+});