feat: add Progressive Web App (PWA) support with service worker registration, manifest, update notifications, and install prompts

frontend/app.js

@@ -5271,5 +5271,89 @@
     safeCreateIcons();
   }
 
-  document.addEventListener("DOMContentLoaded", init);
+  // ---------------------------------------------------------------------------
+  // PWA Service Worker Registration
+  // ---------------------------------------------------------------------------
+  function registerServiceWorker() {
+    if ('serviceWorker' in navigator) {
+      window.addEventListener('load', () => {
+        navigator.serviceWorker.register('/sw.js')
+          .then((registration) => {
+            console.log('[PWA] Service Worker registered successfully:', registration.scope);
+            
+            // Check for updates periodically
+            setInterval(() => {
+              registration.update();
+            }, 60000); // Check every minute
+            
+            // Handle service worker updates
+            registration.addEventListener('updatefound', () => {
+              const newWorker = registration.installing;
+              newWorker.addEventListener('statechange', () => {
+                if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
+                  // New service worker available
+                  showUpdateNotification();
+                }
+              });
+            });
+          })
+          .catch((error) => {
+            console.log('[PWA] Service Worker registration failed:', error);
+          });
+      });
+    }
+  }
+
+  function showUpdateNotification() {
+    const message = document.createElement('div');
+    message.className = 'pwa-update-notification';
+    message.innerHTML = `
+      <div class="pwa-update-content">
+        <span>Une nouvelle version d'ObsiGate est disponible !</span>
+        <button class="pwa-update-btn" onclick="window.location.reload()">Mettre à jour</button>
+        <button class="pwa-update-dismiss" onclick="this.parentElement.parentElement.remove()">×</button>
+      </div>
+    `;
+    document.body.appendChild(message);
+    
+    // Auto-dismiss after 30 seconds
+    setTimeout(() => {
+      if (message.parentElement) {
+        message.remove();
+      }
+    }, 30000);
+  }
+
+  // Handle install prompt
+  let deferredPrompt;
+  window.addEventListener('beforeinstallprompt', (e) => {
+    e.preventDefault();
+    deferredPrompt = e;
+    
+    // Show install button if desired
+    const installBtn = document.getElementById('pwa-install-btn');
+    if (installBtn) {
+      installBtn.style.display = 'block';
+      installBtn.addEventListener('click', async () => {
+        if (deferredPrompt) {
+          deferredPrompt.prompt();
+          const { outcome } = await deferredPrompt.userChoice;
+          console.log(`[PWA] User response to install prompt: ${outcome}`);
+          deferredPrompt = null;
+          installBtn.style.display = 'none';
+        }
+      });
+    }
+  });
+
+  // Log when app is installed
+  window.addEventListener('appinstalled', () => {
+    console.log('[PWA] ObsiGate has been installed');
+    showToast('ObsiGate installé avec succès !');
+  });
+
+  document.addEventListener("DOMContentLoaded", () => {
+    init();
+    registerServiceWorker();
+  });
 })();