fix(create): surface submit errors and fix keyboard overlap on mobile

The create-proposal submit had no error handling, so failures (e.g.
crypto.subtle unavailable outside a secure context) silently reset the
button with no feedback. Also set interactiveWidget so the mobile
keyboard resizes the layout instead of covering the sticky submit button.

src/app/create/CreateClient.tsx

@@ -55,6 +55,11 @@ export default function CreateClient() {
 
   async function handleSubmit(data: ProposalFormData, _publish: boolean) {
     setError('');
+    if (typeof crypto === 'undefined' || !crypto.subtle) {
+      setError('Your browser blocked secure encryption here (this page needs HTTPS). Try opening the site directly instead of through an in-app browser.');
+      return;
+    }
+    try {
       const key = await generateKey();
       const payload = await encryptPayload(key, data);
       const res = await fetch('/api/proposals/guest', {
@@ -71,6 +76,9 @@ export default function CreateClient() {
         publicUrl: `${json.publicUrl}#k=${key}`,
         manageUrl: `${json.manageUrl}#k=${key}`,
       });
+    } catch {
+      setError('Something went wrong creating your proposal. Please try again.');
+    }
   }
 
   function copyLink(url: string) {

src/app/layout.tsx

@@ -42,6 +42,7 @@ export const viewport: Viewport = {
   themeColor: '#ec4899',
   width: 'device-width',
   initialScale: 1,
+  interactiveWidget: 'resizes-content',
 };
 
 export default function RootLayout({ children }: { children: React.ReactNode }) {