feat(web): externalize telemetry URL via environment variables

Replace the hardcoded Nginx proxy configuration with a dynamic environment variable approach. This allows the telemetry dashboard to be loaded via a public URL instead of relying on a local Tailscale proxy.

- Add `VITE_TELEMETRY_URL` build argument to Dockerfile
- Pass `VITE_TELEMETRY_URL` through GitHub Actions deployment workflow
- Remove `/telemetry/` location block from nginx.conf
- Update `TelemetryPage` to use the new environment variable and improve iframe loading state management

.github/workflows/deploy.yml

@@ -77,6 +77,7 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
           build-args: |
             VITE_API_BASE_URL=${{ env.VITE_API_BASE_URL }}
+            VITE_TELEMETRY_URL=${{ vars.VITE_TELEMETRY_URL || 'https://telemetry.zeavisedu.asepharyana.my.id' }}
           cache-from: type=gha,scope=${{ matrix.service.name }}
           cache-to: type=gha,mode=max,scope=${{ matrix.service.name }}