feat: admin users can view all downloads with user badges

- Admin users (Emby IsAdministrator) see a 'Show all users' toggle
- When toggled, all tagged downloads are shown regardless of user
- Each download card shows the tagged user's name as a badge
- Non-admin users see only their own downloads (unchanged behavior)
- Backend accepts ?showAll=true query param (admin-only)

public/style.css

@@ -577,6 +577,42 @@ body {
   background: var(--accent-hover);
 }
 
+/* ===== Admin Controls ===== */
+.admin-controls {
+  display: flex;
+  align-items: center;
+}
+
+.toggle-label {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  cursor: pointer;
+  font-size: 0.8rem;
+  color: var(--text-secondary);
+  background: var(--surface-alt);
+  padding: 4px 12px;
+  border-radius: 14px;
+}
+
+.toggle-label input[type="checkbox"] {
+  width: 14px;
+  height: 14px;
+  cursor: pointer;
+  accent-color: var(--accent);
+}
+
+.download-user-badge {
+  padding: 2px 8px;
+  border-radius: 10px;
+  font-size: 0.65rem;
+  font-weight: 600;
+  text-transform: capitalize;
+  background: var(--accent-light);
+  color: var(--accent);
+  margin-left: auto;
+}
+
 /* ===== Mobile ===== */
 @media (max-width: 768px) {
   .app-header {