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.

src/client/rum.ts

@@ -0,0 +1,41 @@
+// RUM issue capture: forwards client-side errors into the OpenTelemetry RUM
+// pipeline (window.OtelRUM is loaded from otel.k6n.net in index.html).
+
+export function captureRumIssue(
+  message: string,
+  severity = 'ERROR',
+  extra: Record<string, unknown> = {},
+): void {
+  const rum = (globalThis as Record<string, any>).OtelRUM?.last;
+  if (!rum || typeof rum.captureMessage !== 'function') return;
+  try {
+    rum.captureMessage(message, severity, extra);
+  } catch (err) {
+    console.warn('RUM capture failed', err);
+  }
+}
+
+export function installGlobalErrorHandlers(): void {
+  window.addEventListener('error', (event) => {
+    captureRumIssue(event.message || 'Unhandled browser error', 'ERROR', {
+      source: event.filename,
+      line: event.lineno,
+      column: event.colno,
+    });
+  });
+
+  window.addEventListener('unhandledrejection', (event) => {
+    const reason = (event as PromiseRejectionEvent).reason;
+    captureRumIssue(`Unhandled promise rejection: ${reason?.message || reason || 'unknown error'}`, 'ERROR', {
+      name: reason?.name,
+      stack: reason?.stack,
+    });
+  });
+}
+
+/** Trace headers for fetches so server spans link to the browser trace. */
+export function rumTraceHeaders(): Record<string, string> {
+  const rum = (window as Record<string, any>).rum;
+  if (rum && typeof rum.traceHeaders === 'function') return rum.traceHeaders() || {};
+  return {};
+}