feat: Implement full-page loader with progress bar

Co-authored-by: mathieumoran1 <[email protected]>

public/css/app.css

@@ -49,4 +49,73 @@ footer {
   @keyframes loading-dot {
     0%, 80%, 100% { opacity: 0.2; }
     40% { opacity: 1; }
+  }
+
+  /* Full-page loader overlay (blur + progress bar) */
+  body.page-loading {
+    overflow: hidden;
+  }
+
+  .page-loader-overlay {
+    position: fixed;
+    inset: 0;
+    z-index: 2000;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    padding: 24px;
+    background: rgba(255, 255, 255, 0.55);
+    backdrop-filter: blur(10px);
+    -webkit-backdrop-filter: blur(10px);
+    transition: opacity 200ms ease;
+    opacity: 1;
+  }
+
+  .page-loader-overlay.page-loader-hide {
+    opacity: 0;
+    pointer-events: none;
+  }
+
+  .page-loader-card {
+    width: min(520px, 92vw);
+    background: rgba(255, 255, 255, 0.9);
+    border: 1px solid rgba(0, 0, 0, 0.08);
+    border-radius: 16px;
+    padding: 18px 18px 14px;
+    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.12);
+  }
+
+  .page-loader-title {
+    margin: 0 0 10px 0;
+    font-weight: 700;
+    font-size: 1rem;
+    color: #111;
+  }
+
+  .page-loader-subtitle {
+    margin: 0 0 12px 0;
+    font-size: 0.9rem;
+    color: rgba(0, 0, 0, 0.7);
+  }
+
+  .page-loader-progress {
+    height: 10px;
+    border-radius: 999px;
+    overflow: hidden;
+    background: rgba(0, 0, 0, 0.08);
+  }
+
+  .page-loader-bar {
+    height: 100%;
+    width: 0%;
+    border-radius: 999px;
+    background: linear-gradient(90deg, #ff4d4d 0%, #ffb200 50%, #4cd964 100%);
+    transition: width 220ms ease;
+  }
+
+  .page-loader-actions {
+    margin-top: 12px;
+    display: flex;
+    justify-content: flex-end;
+    gap: 10px;
   }