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/server/tracing.ts

@@ -0,0 +1,75 @@
+// OpenTelemetry tracing and logging initialization for the gibbz backend.
+// Loaded before HTTP / network modules start serving traffic.
+import process from 'node:process';
+import { NodeSDK } from '@opentelemetry/sdk-node';
+import { getNodeAutoInstrumentations } from '@opentelemetry/auto-instrumentations-node';
+import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-http';
+import { OTLPLogExporter } from '@opentelemetry/exporter-logs-otlp-http';
+import { BatchLogRecordProcessor } from '@opentelemetry/sdk-logs';
+import { resourceFromAttributes } from '@opentelemetry/resources';
+import { ATTR_SERVICE_NAME, ATTR_SERVICE_VERSION } from '@opentelemetry/semantic-conventions';
+
+export class Tracing {
+  private sdk: NodeSDK | undefined;
+
+  start(
+    env: Record<string, string | undefined> = process.env,
+    onFatal?: (err: unknown) => void,
+  ): void {
+    const serviceName = env.OTEL_SERVICE_NAME || 'gibbz';
+    const serviceRelease = env.SERVICE_RELEASE || env.OTEL_SERVICE_RELEASE || env.APP_RELEASE || 'dev';
+    const environment = env.ENVIRONMENT || env.NODE_ENV || 'production';
+    const otelUrl = (env.OTEL_EXPORTER_OTLP_ENDPOINT || env.OTEL_URL || 'https://otel.k6n.net').replace(/\/+$/, '');
+    const ingestKey = env.OTEL_INGEST_KEY || '';
+
+    const headers: Record<string, string> = {};
+    if (ingestKey) headers['X-Otel-Ingest-Key'] = ingestKey;
+
+    const resource = resourceFromAttributes({
+      [ATTR_SERVICE_NAME]: serviceName,
+      [ATTR_SERVICE_VERSION]: serviceRelease,
+      'service.release': serviceRelease,
+      'service.environment': environment,
+    });
+
+    const sdk = new NodeSDK({
+      resource,
+      traceExporter: new OTLPTraceExporter({ url: `${otelUrl}/v1/traces`, headers }),
+      logRecordProcessor: new BatchLogRecordProcessor({
+        exporter: new OTLPLogExporter({ url: `${otelUrl}/v1/logs`, headers }),
+      }),
+      instrumentations: [
+        getNodeAutoInstrumentations({
+          '@opentelemetry/instrumentation-fs': { enabled: false },
+        }),
+      ],
+    });
+    this.sdk = sdk;
+
+    try {
+      sdk.start();
+      console.log(
+        `[otel] Initialized OpenTelemetry for ${serviceName} (release: ${serviceRelease}, env: ${environment}) -> ${otelUrl}`,
+      );
+    } catch (err) {
+      console.error('[otel] Failed to start OpenTelemetry SDK:', err);
+      onFatal?.(err);
+    }
+
+    process.on('SIGTERM', () => {
+      this.shutdown()
+        .then(() => {
+          console.log('[otel] SDK shut down successfully');
+          process.exit(0);
+        })
+        .catch((err) => {
+          console.error('[otel] Error shutting down SDK', err);
+          process.exit(0);
+        });
+    });
+  }
+
+  async shutdown(): Promise<void> {
+    await this.sdk?.shutdown();
+  }
+}