feat: Ajout d'un spinner pendant l'initialisation du Service Worker

- Spinner avec message explicatif 'Initializing database service...'
- Affiché après l'enregistrement du Service Worker
- Masqué automatiquement une fois le service prêt
- Design glassmorphism cohérent avec l'interface
- Z-index élevé (10000) pour être au-dessus de tout
- Animation de rotation fluide
- Feedback utilisateur pendant l'attente

src/services/database.service.ts

@@ -120,6 +120,9 @@ export class Database {
         // No existing workers: register a new one.
         this.serviceWorkerRegistration = await navigator.serviceWorker.register(path, { type: 'module' });
         console.log('Service Worker registered with scope:', this.serviceWorkerRegistration.scope);
+        
+        // Show spinner during service worker initialization
+        this.showServiceWorkerSpinner('Initializing database service...');
       } else if (registrations.length === 1) {
         // One existing worker: update it (restart it) without unregistering.
         this.serviceWorkerRegistration = registrations[0];
@@ -132,10 +135,16 @@ export class Database {
         console.log('All previous Service Workers unregistered.');
         this.serviceWorkerRegistration = await navigator.serviceWorker.register(path, { type: 'module' });
         console.log('Service Worker registered with scope:', this.serviceWorkerRegistration.scope);
+        
+        // Show spinner during service worker initialization
+        this.showServiceWorkerSpinner('Initializing database service...');
       }
 
       await this.checkForUpdates();
 
+      // Hide spinner once service worker is ready
+      this.hideServiceWorkerSpinner();
+
       // Set up a global message listener for responses from the service worker.
       navigator.serviceWorker.addEventListener('message', async (event) => {
         console.log('Received message from service worker:', event.data);
@@ -449,6 +458,101 @@ export class Database {
       throw e;
     }
   }
+
+  private showServiceWorkerSpinner(message: string = 'Initializing...') {
+    // Remove existing spinner if any
+    this.hideServiceWorkerSpinner();
+    
+    // Create spinner overlay
+    const overlay = document.createElement('div');
+    overlay.id = 'service-worker-spinner-overlay';
+    overlay.style.cssText = `
+      position: fixed;
+      top: 0;
+      left: 0;
+      width: 100%;
+      height: 100%;
+      background: rgba(0, 0, 0, 0.8);
+      display: flex;
+      flex-direction: column;
+      justify-content: center;
+      align-items: center;
+      z-index: 10000;
+      backdrop-filter: blur(5px);
+    `;
+    
+    // Create spinner content
+    const spinnerContent = document.createElement('div');
+    spinnerContent.style.cssText = `
+      background: rgba(255, 255, 255, 0.95);
+      border-radius: 12px;
+      padding: 30px;
+      text-align: center;
+      box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
+      border: 1px solid rgba(255, 255, 255, 0.2);
+      max-width: 400px;
+      width: 90%;
+    `;
+    
+    // Create spinner
+    const spinner = document.createElement('div');
+    spinner.style.cssText = `
+      width: 40px;
+      height: 40px;
+      border: 3px solid #f3f3f3;
+      border-top: 3px solid #3a506b;
+      border-radius: 50%;
+      animation: spin 1s linear infinite;
+      margin: 0 auto 15px auto;
+    `;
+    
+    // Create message
+    const messageEl = document.createElement('div');
+    messageEl.textContent = message;
+    messageEl.style.cssText = `
+      font-size: 14px;
+      color: #3a506b;
+      font-weight: 500;
+      margin-bottom: 10px;
+    `;
+    
+    // Create progress indicator
+    const progressEl = document.createElement('div');
+    progressEl.textContent = 'Please wait...';
+    progressEl.style.cssText = `
+      font-size: 12px;
+      color: #666;
+    `;
+    
+    // Add CSS animation if not already present
+    if (!document.getElementById('service-worker-spinner-styles')) {
+      const style = document.createElement('style');
+      style.id = 'service-worker-spinner-styles';
+      style.textContent = `
+        @keyframes spin {
+          0% { transform: rotate(0deg); }
+          100% { transform: rotate(360deg); }
+        }
+      `;
+      document.head.appendChild(style);
+    }
+    
+    // Assemble spinner
+    spinnerContent.appendChild(spinner);
+    spinnerContent.appendChild(messageEl);
+    spinnerContent.appendChild(progressEl);
+    overlay.appendChild(spinnerContent);
+    
+    // Add to document
+    document.body.appendChild(overlay);
+  }
+
+  private hideServiceWorkerSpinner() {
+    const overlay = document.getElementById('service-worker-spinner-overlay');
+    if (overlay) {
+      overlay.remove();
+    }
+  }
 }
 
 export default Database;