- 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
Previously the CreateCertificate handler checked domain existence and then
inserted separately, creating a race window where concurrent requests could
both pass the check and trigger 'UNIQUE constraint failed' on INSERT.
Now uses SQLite's native INSERT ... ON CONFLICT (upsert) which atomically
handles the uniqueness constraint at the database level, eliminating the
race condition entirely.
cnbugs