feat: deploy admin panel to stage

STAGE_DEPLOYMENT.md

@@ -0,0 +1,22 @@
+# Stage deployment
+
+The admin panel is a static Vite bundle. The backend and device remain
+separate services.
+
+Build a stage image with the service URLs embedded into the bundle:
+
+```bash
+docker build \
+  --build-arg VITE_API_URL=https://server.white-nights-stage.makkah.verstack.ru \
+  --build-arg VITE_KRBL_MEDIA=https://server.white-nights-stage.makkah.verstack.ru/media/ \
+  --build-arg VITE_GEO_API_URL=https://device.white-nights-stage.makkah.verstack.ru \
+  --build-arg VITE_WEATHER_API_URL=https://device.white-nights-stage.makkah.verstack.ru \
+  -t white-nights-admin-panel:stage .
+```
+
+The backend URL serves content, authentication, media and admin API requests.
+The device URL serves geolocation and weather requests used by `/demo/:id`.
+
+The device ingress must publish the geolocation and weather paths to the
+corresponding device ports. The browser must also be authorized by Authelia
+and the backend must allow the frontend origin through CORS.