* feat(security): warn when ActiveRecord encryption is not configured
Self-hosted instances without explicit ACTIVE_RECORD_ENCRYPTION_* keys (or Rails credentials) store sensitive columns - API keys, provider/bank tokens, the MFA (TOTP) secret, and PII - unencrypted at rest. The app boots and works normally so this plaintext at rest state is easy to miss.
Change: Make it visible:
- log a clear startup warning (config/initializers/encryption_warning.rb)
- show a warning banner on /settings/security when encryption is unconfigured
* refactor(security): apply review feedback on encryption warning
- list the three ACTIVE_RECORD_ENCRYPTION_* keys in the banner, rendered via the DS::Alert content block to match the log
- drop the redundant respond_to?(:self_hosted?) guard in the initializer so it matches the controller check
- add a managed-mode test asserting the banner is hidden
