feat: Add PWA support and CORS configuration

- Configure VitePWA with manifest, icons and service worker
- Add PwaInstallBanner component for install prompt in header
- Enable CORS for z590.interno.com access
- Use dynamic hostname for terminal WebSocket connection
- Add generate-icons script with sharp for PWA icons
- Fix theme-color to match header background

frontend/src/styles/main.css

@@ -18,15 +18,20 @@
 
 html, body {
   height: 100%;
+  min-height: 100vh;
+  min-height: 100dvh;
   font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
-  background: var(--bg-primary);
+  background: var(--bg-secondary);
   color: var(--text-primary);
   -webkit-font-smoothing: antialiased;
   -moz-osx-font-smoothing: grayscale;
+  overflow: hidden;
 }
 
 #app {
   height: 100%;
+  min-height: 100vh;
+  min-height: 100dvh;
 }
 
 /* Scrollbar styling */