Simplify recipient emails and add live upload progress on create.

Recipients always get the download link immediately when an email is set.
Large files upload in the background with per-file and overall progress bars.

Co-authored-by: Cursor <cursoragent@cursor.com>

resources/css/app.css

@@ -15,6 +15,41 @@
     display: none !important;
 }
 
+@keyframes upload-progress-shimmer {
+    0% {
+        transform: translateX(-100%);
+    }
+
+    100% {
+        transform: translateX(100%);
+    }
+}
+
+.upload-progress-track {
+    height: 0.375rem;
+    width: 100%;
+    overflow: hidden;
+    border-radius: 9999px;
+    background-color: rgb(226 232 240);
+}
+
+.upload-progress-bar {
+    position: relative;
+    height: 100%;
+    border-radius: 9999px;
+    background: linear-gradient(90deg, #6366f1 0%, #4f46e5 100%);
+    transition: width 0.25s ease;
+    overflow: hidden;
+}
+
+.upload-progress-bar::after {
+    content: '';
+    position: absolute;
+    inset: 0;
+    background: linear-gradient(90deg, transparent, rgb(255 255 255 / 0.35), transparent);
+    animation: upload-progress-shimmer 1.4s ease-in-out infinite;
+}
+
 /* QR create/show: flush mobile action bar to the physical screen bottom (mobile only) */
 @media (max-width: 1023px) {
     .mobile-action-bar {