feat: Add PWA support for mobile app-like experience

Add manifest.json and meta tags to enable:
- Add to Home Screen on iOS/Android
- Standalone mode (no browser UI)
- Custom app icon and theme color

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

reports-app/frontend/public/manifest.json

@@ -0,0 +1,24 @@
+{
+  "name": "ROA Reports",
+  "short_name": "ROA",
+  "description": "Rapoarte ERP - facturi și încasări",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#2563eb",
+  "orientation": "portrait-primary",
+  "icons": [
+    {
+      "src": "/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any maskable"
+    },
+    {
+      "src": "/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ]
+}