🔒 security(auth): migrate to EdDSA JWT and add automated monitoring

BREAKING: JWT keys are now auto-managed by Better Auth (EdDSA/Ed25519)
- Remove all JWT_PRIVATE_KEY, JWT_PUBLIC_KEY, JWT_SECRET references
- Keys stored in auth.jwks database table (auto-generated on first run)
- Delete obsolete generate-keys.sh and generate-staging-secrets.sh scripts
- Clean up legacy AUTH_*.md analysis files from root

Security Improvements:
- Add security_events table for audit logging
- Add SecurityEventsService for tracking auth events
- Enhanced security headers (HSTS, CSP, X-Frame-Options)
- Rate limiting configuration

Monitoring Setup:
- Add auth-health-check.sh for automated testing
- Add generate-dashboard.sh for HTML status dashboard
- Tests: health endpoint, JWKS (EdDSA), security headers, response time
- Ready for Hetzner cron deployment

Documentation:
- Update deployment docs with Better Auth notes
- Update environment variable references
- Add security improvements documentation

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.dev.yml

@@ -99,8 +99,7 @@ services:
       REDIS_HOST: redis
       REDIS_PORT: 6379
       REDIS_PASSWORD: ${REDIS_PASSWORD:-devpassword}
-      JWT_PUBLIC_KEY: ${JWT_PUBLIC_KEY}
-      JWT_PRIVATE_KEY: ${JWT_PRIVATE_KEY}
+      # JWT keys managed automatically by Better Auth (EdDSA) - stored in auth.jwks table
       JWT_ACCESS_TOKEN_EXPIRY: ${JWT_ACCESS_TOKEN_EXPIRY:-15m}
       JWT_REFRESH_TOKEN_EXPIRY: ${JWT_REFRESH_TOKEN_EXPIRY:-7d}
       JWT_ISSUER: ${JWT_ISSUER:-manacore}