security: remove exposed credentials and CLAUDE.md from repository

- Replace real Supabase token in README.md with placeholder
- Remove CLAUDE.md from repository (should be gitignored)
- Add CLAUDE.md and .claude/ to .gitignore
- Addresses security disclosure from Supabase security team

Author: ringo380

.gitignore

@@ -4,3 +4,5 @@ dist/
 .temp/
 .DS_Store
 .env*
+CLAUDE.md
+.claude/