Add Docker Compose stack and Pi notes

LiveKit on host networking so WebRTC can advertise a reachable address,
plus the server and website.

infra/.env.example

@@ -0,0 +1,16 @@
+LIVEKIT_API_KEY=devkey
+LIVEKIT_API_SECRET=devsecretdevsecretdevsecretdevsecret
+
+PUBLIC_LIVEKIT_URL=ws://localhost:7880
+PUBLIC_API_URL=http://localhost:8080
+
+SESSION_SECRET=change-me-to-a-long-random-string
+SESSION_TTL_HOURS=12
+
+BOOTSTRAP_ADMIN_EMAIL=admin@pistation.local
+BOOTSTRAP_ADMIN_PASSWORD=changeme
+
+PIN_ROTATION_SECONDS=45
+PIN_GRACE_SECONDS=15
+
+CORS_ORIGINS=http://localhost:3000,http://localhost:5173