Reapply "Add missing admin action files and navigation links"

This reverts commit 4d515bc400.

src/app/admin/loading.tsx

@@ -1,7 +1,10 @@
 export default function AdminLoading() {
   return (
     <div style={{ display: "flex", justifyContent: "center", padding: "4rem 0" }}>
-      <div className="animate-spin w-8 h-8 border-4 rounded-full" style={{ borderColor: "var(--color-primary)", borderTopColor: "transparent" }} />
+      <div
+        className="animate-spin w-8 h-8 border-4 rounded-full"
+        style={{ borderColor: "var(--color-primary)", borderTopColor: "transparent" }}
+      />
     </div>
   );
 }