Neon / portal template support (#713)

TODOs:
- [x] Do restart when checkout / restore if there is a DB
- [x] List all branches (branch id, name, date)
- [x] Allow checking out versions with no DB
- [x] safeguard to never delete main branches
- [x] create app hook for neon template
- [x] weird UX with connector on configure panel
- [x] tiny neon logo in connector
- [x] deploy to vercel
- [x] build forgot password page
- [x] what about email setup
- [x] lots of imgix errors
- [x] edit file - db snapshot
- [x] DYAD_DISABLE_DB_PUSH
- [ ] update portal doc
- [x] switch preview branch to be read-only endpoint
- [x] disable supabase sys prompt if neon is enabled
- [ ] https://payloadcms.com/docs/upload/storage-adapters
- [x] need to use main branch...

Phase 2?
- [x] generate DB migrations

src/components/preview_panel/PreviewIframe.tsx

@@ -413,7 +413,20 @@ export const PreviewIframe = ({ loading }: { loading: boolean }) => {
 
   // Display loading state
   if (loading) {
-    return <div className="p-4 dark:text-gray-300">Loading app preview...</div>;
+    return (
+      <div className="flex flex-col h-full relative">
+        <div className="absolute inset-0 flex flex-col items-center justify-center space-y-4 bg-gray-50 dark:bg-gray-950">
+          <div className="relative w-5 h-5 animate-spin">
+            <div className="absolute top-0 left-1/2 transform -translate-x-1/2 w-2 h-2 bg-primary rounded-full"></div>
+            <div className="absolute bottom-0 left-0 w-2 h-2 bg-primary rounded-full opacity-80"></div>
+            <div className="absolute bottom-0 right-0 w-2 h-2 bg-primary rounded-full opacity-60"></div>
+          </div>
+          <p className="text-gray-600 dark:text-gray-300">
+            Preparing app preview...
+          </p>
+        </div>
+      </div>
+    );
   }
 
   // Display message if no app is selected
@@ -565,7 +578,7 @@ export const PreviewIframe = ({ loading }: { loading: boolean }) => {
           <div className="absolute inset-0 flex flex-col items-center justify-center space-y-4 bg-gray-50 dark:bg-gray-950">
             <Loader2 className="w-8 h-8 animate-spin text-gray-400 dark:text-gray-500" />
             <p className="text-gray-600 dark:text-gray-300">
-              Starting up your app...
+              Starting your app server...
             </p>
           </div>
         ) : (