fix(middleware): improve case-insensitive env mode checking

Simplify the local mode detection logic by using toLowerCase() instead
of explicit case matching. This makes the code more robust and handles
any case variation of NEXT_PUBLIC_ENV_MODE consistently.

The setup.py script generates "LOCAL" (uppercase) while developers
might use "local" (lowercase), so this ensures both work reliably.

frontend/src/middleware.ts

@@ -66,7 +66,7 @@ export async function middleware(request: NextRequest) {
       return NextResponse.redirect(url);
     }
 
-    const isLocalMode = process.env.NEXT_PUBLIC_ENV_MODE === 'local'
+    const isLocalMode = process.env.NEXT_PUBLIC_ENV_MODE?.toLowerCase() === 'local'
     if (isLocalMode) {
       return supabaseResponse;
     }