feat: close buttons as a red cross in a square; static files revalidated by content, so a release reaches the browser at once

internal/server/web/static/app.css

@@ -65,6 +65,9 @@ button:hover, .btn:hover { background: var(--accent-hover); text-decoration: non
 /* Close buttons: red text and border on the ghost button. */
 .btn.close, .btn.ghost.close { background: transparent; border: 1px solid rgba(255, 92, 92, .6); color: var(--danger); }
 .btn.close:hover, .btn.ghost.close:hover { background: #3a1d1d; border-color: var(--danger); }
+/* A close button that is just a cross: square, the height of the buttons by it. */
+.btn.close.x { width: 32px; height: 32px; padding: 0; display: inline-flex; align-items: center; justify-content: center; }
+.btn.small.close.x { width: 28px; height: 28px; }
 .btn.small { padding: 6px 10px; font-size: 13px; }
 .btn.icon { width: 30px; height: 30px; padding: 0; display: inline-flex;
   align-items: center; justify-content: center; font-size: 14px; line-height: 1; text-decoration: none; }