feat(ebook): improve search UX with grid actions and Enter-to-submit

Add a two-column grid layout for the admin protected-phrases actions
and submit the search form on Enter (Shift+Enter for newline).

python/ebook_search/api/static/style.css

@@ -218,6 +218,11 @@ button:hover {
     margin-bottom: 24px;
 }
 
+.actions-grid {
+    display: grid;
+    grid-template-columns: repeat(2, max-content);
+}
+
 /* Answer + results */
 #results {
     display: block;