fix: return JSON error responses from upload-attachment API

Error responses were returned as plain text, causing the frontend to fail JSON parsing and display "Unknown error (400)" instead of the actual error message. Also distinguish between empty and invalid wallet address in error messages for better debugging.

Author: rareboe

app/routes/api.upload-attachment.ts

@@ -59,31 +59,45 @@ async function imageUploadAction({ context, request }: ActionFunctionArgs) {
     const verse = formData.get('verse') as string;
 
     if (!file || !path) {
-      throw new Response('Missing required fields: file, path', { status: 400, statusText: 'Bad Request' });
+      throw new Response(JSON.stringify({ success: false, error: 'Missing required fields: file, path' }), {
+        status: 400,
+        headers: { 'Content-Type': 'application/json' },
+      });
     }
 
     const { accessToken, walletAddress } = context.user as ContextUser;
 
     if (!accessToken) {
-      throw new Response('Unauthorized (no access token)', { status: 401, statusText: 'Unauthorized' });
+      throw new Response(JSON.stringify({ success: false, error: 'Unauthorized (no access token)' }), {
+        status: 401,
+        headers: { 'Content-Type': 'application/json' },
+      });
     }
 
     const isChatUpload = path === CHAT_UPLOADS_PATH;
     const verseId = isChatUpload ? walletAddress : verse;
 
     if (!verseId) {
-      throw new Response(isChatUpload ? 'User wallet address is not available' : 'Missing required field: verse', {
+      let error: string;
+
+      if (isChatUpload) {
+        error = walletAddress ? `Invalid wallet address: ${walletAddress}` : 'User wallet address is empty';
+      } else {
+        error = 'Missing required field: verse';
+      }
+
+      throw new Response(JSON.stringify({ success: false, error }), {
         status: 400,
-        statusText: 'Bad Request',
+        headers: { 'Content-Type': 'application/json' },
       });
     }
 
     const endpoint = env.V8_GAMESERVER_ENDPOINT;
 
     if (!endpoint) {
-      throw new Response('Game server endpoint is not configured', {
+      throw new Response(JSON.stringify({ success: false, error: 'Game server endpoint is not configured' }), {
         status: 500,
-        statusText: 'Internal Server Error',
+        headers: { 'Content-Type': 'application/json' },
       });
     }