feat: update frontend to work with v2 backend — camelCase, new endpoints, nested author

thoughts-frontend/components/reply-form.tsx

@@ -33,8 +33,8 @@ export function ReplyForm({ parentThoughtId, onReplySuccess }: ReplyFormProps) {
     resolver: zodResolver(CreateThoughtSchema),
     defaultValues: {
       content: "",
-      replyToId: parentThoughtId,
-      visibility: "Public", // Replies default to Public
+      inReplyToId: parentThoughtId,
+      visibility: "public",
     },
   });