fix: Use ATproto localhost OAuth development mode

- Changed BLUESKY_CLIENT_ID to use http://localhost/ with redirect_uri parameter
- Updated magnitude.config.ts to use localhost:3000 for testing
- Removed public/client-metadata.json (no longer needed with localhost mode)
- Updated OAuth test to expect successful redirect to bsky.social

This leverages ATproto's special localhost client development mode which allows
local OAuth testing without requiring client metadata files.

See: https://atproto.com/specs/oauth#localhost-client-development

🤖 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',
-  // Use 127.0.0.1 instead of localhost per RFC 8252 for OAuth
-  url: 'http://127.0.0.1:3000',
+  // Use localhost for ATproto OAuth localhost development mode
+  url: 'http://localhost:3000',
   // We will configure magnitude to find tests in this directory
   tests: 'tests/magnitude/**/*.mag.ts',
 };