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>

.example.env

@@ -14,8 +14,9 @@ GOOGLE_AI_API_KEY=your-google-ai-api-key
 # Deepgram API Key (for voice-to-text)
 DEEPGRAM_API_KEY=your-deepgram-api-key
 
-# Bluesky/ATproto OAuth Configuration (use 127.0.0.1 per RFC 8252)
-BLUESKY_CLIENT_ID=http://127.0.0.1:3000/client-metadata.json
+# Bluesky/ATproto OAuth Configuration (localhost development mode)
+# See: https://atproto.com/specs/oauth#localhost-client-development
+BLUESKY_CLIENT_ID=http://localhost/?redirect_uri=http://127.0.0.1:3000/api/auth/callback
 BLUESKY_REDIRECT_URI=http://127.0.0.1:3000/api/auth/callback
 
 # Test Account Credentials (for E2E tests)