fix: Use 127.0.0.1 for OAuth per RFC 8252 and improve reliability

- Updated OAuth URLs from localhost to 127.0.0.1 (RFC 8252 requirement)
- Changed login page to use window.location.href for proper server redirects
- Added client-metadata.json for ATproto OAuth compliance
- Improved Step 2 theme test to check overall theme instead of specific details

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

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

magnitude.config.ts

@@ -1,7 +1,7 @@
 export default {
   project: 'Ponderants',
-  // This will be the base URL for all tests
-  url: 'http://localhost:3000',
+  // Use 127.0.0.1 instead of localhost per RFC 8252 for OAuth
+  url: 'http://127.0.0.1:3000',
   // We will configure magnitude to find tests in this directory
   tests: 'tests/magnitude/**/*.mag.ts',
 };