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.

Makefile

@@ -11,13 +11,15 @@ all: check
 help: ## Show target help
 	@grep -E '^[a-zA-Z_-]+:.*?## ' $(MAKEFILE_LIST) | awk 'BEGIN{FS=":.*?## "}{printf "  \033[36m%-16s\033[0m %s\n", $$1, $$2}'
 
-test: ## Run local tests
-	npm test
+test: ## Run tests (bun test)
+	bun test
 
-check: test ## Quality gate: run all tests
+check: test ## Quality gate: tests + typecheck
+	bun run typecheck
 
-build: check ## Build local dependencies and run tests
-	npm ci
+build: check ## Install deps and build the client bundle
+	bun install
+	bun run build
 
 docker-build: ## Build docker image
 	docker build \