- New config/credential_store.go: persistent credential storage (credentials.json)
- New API: CRUD for DNS credentials + credential-types endpoint
- Certificate model now supports credential_id reference
- Create certificate auto-resolves credential_id to DNS config
- New Vue page: Credentials.vue for managing saved DNS keys
- CertCreate.vue: select existing credential or manual input + save as new
- Secrets masked in API responses, never exposed in list
- Remove GORM and SQLite, use simple JSON file (data/certs.json) for persistence
- CertStore with sync.RWMutex for thread-safe in-memory cache
- All handlers updated to use config.Store instead of config.DB
- Cron job and stats updated accordingly
- go mod tidy removes unused gorm/sqlite dependencies