Scaffold plant app - MQTT monitoring for boiler-room equipment

Read-only monitoring/alerting for boilers, water softener, calorifiers
and pumps via a generic MQTT-topic-prefix asset model, so new
equipment can be onboarded without new ingestion code. Threshold and
stale-data alert rules with email + in-app notification.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/vite.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'vite'
+import react from '@vitejs/plugin-react'
+
+export default defineConfig({
+  base: '/plant/',
+  plugins: [react()],
+})