Add ACME DNS-01 (TXT-record) validation alongside the existing HTTP-01,
for internal/isolated clusters with no public port 80 and for wildcard
certificates. Opt-in via a global kill-switch (default off); HTTP-01 is
byte-for-byte unchanged, with zero agent or rendered-config changes.
- Pluggable DNS provider interface (Manual + Cloudflare). Per-account
credentials are Fernet-encrypted at rest, verified on save, and never
returned by the API or written to logs/events/error_detail.
- Non-blocking per-cycle orchestrator: publish (CAS) -> propagation grace
(across cycles, no in-loop sleep) -> respond -> finalize/download, with a
bounded fresh-order retry chain (1 original + 3 retries) on propagation lag.
- Manual flow: user publishes the TXT record and confirms; manual DNS-01
cannot auto-renew unattended (auto-renew forced off and surfaced in the UI).
- Migration v8: additive, idempotent columns on letsencrypt_accounts/orders
and acme_challenges, plus a new letsencrypt_account_dns_credentials table.
- Challenge-type-aware diagnostics (port80/routing/DNS checks skipped for
DNS-01) and a DNS-01 event timeline in the order detail.
- Frontend: DNS-01 account + credentials management, cert wizard adaptation,
order-detail TXT records + verify, orders/renewal Method columns, and a
Settings kill-switch. README, release notes, and API docs updated.
Implements #35.
taylanbakircioglu