feat: prompts admin-only, add isOpen field to Prompt model

app/[locale]/admin/page.tsx

@@ -133,6 +133,7 @@ export default function AdminPage() {
   const [promptDesc, setPromptDesc] = useState('');
   const [promptContent, setPromptContent] = useState('');
   const [promptTagsText, setPromptTagsText] = useState('Next.js, System Prompt');
+  const [promptIsOpen, setPromptIsOpen] = useState(false);
   const [savingPrompt, setSavingPrompt] = useState(false);
 
   // Lesson Form Modal State (Create or Edit)
@@ -386,6 +387,7 @@ export default function AdminPage() {
         description: promptDesc,
         content: promptContent,
         tags,
+        isOpen: promptIsOpen,
       });
     } else {
       res = await createPrompt({
@@ -394,6 +396,7 @@ export default function AdminPage() {
         description: promptDesc,
         content: promptContent,
         tags,
+        isOpen: promptIsOpen,
       });
     }
 
@@ -1295,6 +1298,27 @@ export default function AdminPage() {
                 />
               </div>
 
+              {/* isOpen Toggle */}
+              <div className="flex items-center justify-between p-3 rounded-xl bg-slate-950 border border-slate-800">
+                <div>
+                  <p className="text-xs font-bold text-slate-300">Open (Public Access)</p>
+                  <p className="text-[10px] text-slate-500 mt-0.5">When enabled, this prompt can be made publicly available</p>
+                </div>
+                <button
+                  type="button"
+                  onClick={() => setPromptIsOpen((v) => !v)}
+                  className={`relative inline-flex h-6 w-11 items-center rounded-full transition-colors focus:outline-none ${
+                    promptIsOpen ? 'bg-emerald-500' : 'bg-slate-700'
+                  }`}
+                >
+                  <span
+                    className={`inline-block h-4 w-4 transform rounded-full bg-white shadow transition-transform ${
+                      promptIsOpen ? 'translate-x-6' : 'translate-x-1'
+                    }`}
+                  />
+                </button>
+              </div>
+
               <div className="flex justify-end gap-3 pt-4 border-t border-slate-800">
                 <button
                   type="button"