feat: React 19 SPA frontend (v3.0) — volledige moderne UI op /app

- 24 pagina's: dashboard, clients, engagements, tasks, calendar, email,
  projects, time, invoices, finance, racks (visuele rack-view), networking,
  diagrams, market intel, AI studio (providers+chat), notifications,
  search, settings (algemeen/users/backup/audit)
- Vite + React 19 + Tailwind v4 + recharts + lucide, dark neon thema, NL
- Build gedeployed naar public/spa, geserveerd door Express op /app

frontend/package.json

@@ -0,0 +1,24 @@
+{
+  "name": "mek-tech-spa",
+  "private": true,
+  "version": "3.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "lucide-react": "^0.510.0",
+    "react": "^19.1.0",
+    "react-dom": "^19.1.0",
+    "react-router-dom": "^7.6.0",
+    "recharts": "^2.15.3"
+  },
+  "devDependencies": {
+    "@tailwindcss/vite": "^4.1.7",
+    "@vitejs/plugin-react": "^4.4.1",
+    "tailwindcss": "^4.1.7",
+    "vite": "^6.3.5"
+  }
+}