fix: Resolve Supabase SSR cookie handling and auth test page issues

- Add null checks for cookies object in Supabase SSR client
- Fix auth test page to use Astro.cookies instead of Astro.request
- Prevent "Cannot read properties of undefined" errors in cookie handling
- Ensure proper unified auth usage pattern in test pages

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/pages/auth-test-unified.astro

@@ -11,8 +11,8 @@ let cookies = null;
 let headers = null;
 
 try {
-  // Test unified auth
-  auth = await verifyAuth(Astro.request);
+  // Test unified auth - use Astro.cookies for pages
+  auth = await verifyAuth(Astro.cookies);
   
   // Capture debug info
   cookies = Astro.request.headers.get('Cookie') || 'No cookies';