feat: enhance CSV import functionality, integrate react-query for data fetching, and refactor admin components

frontend/src/components/SubHeaderAdmin.tsx

@@ -3,8 +3,13 @@ import { Sheet, WholeWord } from "lucide-react";
 import { useState } from "react";
 import ImportGUI from "./ImportGUI";
 
+type SubHeaderAdminProps = {
+  setFiles: (files: File[]) => void;
+  files?: File[];
+};
+
 // Sub navigation bar for admin views: provides import + clear selection actions
-const SubHeaderAdmin: React.FC = () => {
+const SubHeaderAdmin: React.FC<SubHeaderAdminProps> = ({ setFiles, files }) => {
   const [showImport, setShowImport] = useState(false);
 
   return (
@@ -48,7 +53,13 @@ const SubHeaderAdmin: React.FC = () => {
           </div>
         </div>
       </header>
-      {showImport && <ImportGUI onClose={() => setShowImport(false)} />}
+      {showImport && (
+        <ImportGUI
+          onClose={() => setShowImport(false)}
+          setFiles={setFiles}
+          files={files}
+        />
+      )}
     </>
   );
 };