refactor: replace server action with API route for image uploads and update Nginx rate limiting configuration

app/form/admin/client.tsx

@@ -18,7 +18,6 @@ import {
   deleteQuestion,
   reorderQuestions,
 } from "@/app/actions/questions";
-import { uploadImage } from "@/app/actions/upload";
 import { Plus, Trash, ArrowUp, ArrowDown, Loader2, Save, Image as ImageIcon, X } from "lucide-react";
 import Image from 'next/image';
 
@@ -146,7 +145,19 @@ export default function FormEditorClient({ form, initialQuestions }: FormEditorC
     setUploadingId(questionId);
     
     toast.promise(
-      uploadImage(formData).then(async (imageUrl) => {
+      new Promise<string>(async (resolve, reject) => {
+        try {
+          const res = await fetch("/api/upload", {
+            method: "POST",
+            body: formData,
+          });
+          const data = await res.json();
+          if (!res.ok) throw new Error(data.error || "Failed to upload image");
+          resolve(data.url);
+        } catch (error) {
+          reject(error);
+        }
+      }).then(async (imageUrl) => {
         await updateQuestion(questionId, form.id, { imageUrl });
         setQuestions((prev) =>
           prev.map((q) => (q.id === questionId ? { ...q, imageUrl } : q))