Add Google sign-in functionality to Login and Register pages, including error handling and UI updates for better user experience.

app/auth/callback/route.ts

@@ -0,0 +1,17 @@
+import { createRouteHandlerClient } from '@supabase/auth-helpers-nextjs';
+import { cookies } from 'next/headers';
+import { NextRequest, NextResponse } from 'next/server';
+
+export async function GET(request: NextRequest) {
+  const requestUrl = new URL(request.url);
+  const code = requestUrl.searchParams.get('code');
+  
+  if (code) {
+    const cookieStore = cookies();
+    const supabase = createRouteHandlerClient({ cookies: () => cookieStore });
+    await supabase.auth.exchangeCodeForSession(code);
+  }
+
+  // URL to redirect to after sign in process completes
+  return NextResponse.redirect(new URL('/analytics', request.url));
+}