Add missing fields to add page

src/main/resources/static/add.css

@@ -171,3 +171,30 @@ form :has(#url) {
 .btn:disabled {
     filter: var(--drop-shadow) grayscale(.5) brightness(.5);
 }
+
+#category[value="new"] {
+    display: none;
+}
+
+label[for="category"] {
+    width: 0;
+    user-select: none;
+    overflow: hidden;
+}
+
+span:has(#category) {
+    gap: unset;
+}
+
+#new-category-group:not(.hidden) {
+    display: flex;
+    justify-content: stretch;
+    gap: var(--gap-small);
+    width: 100%;
+}
+
+#new-category-group button {
+    background-image: url("./sort.svg");
+    background-size: contain;
+    background-origin: content-box;
+}