Replace magic strings across the automation domain with backed PHP enums
(HttpMethod, AuthType, DelayUnit, ScheduleField) and mirrored TS consts
(http-method, auth-type, delay-unit, schedule-field, condition-operator,
publish-mode), plus the existing Condition\Handle / Operator / Publish\Mode.
Also:
- require scheduled_offset via concrete-index required_if instead of
defaulting to 60 when the publish mode is scheduled
- fail the webhook node explicitly when the resolved url is empty
- localize node failure messages (fetch_rss/http/webhook)
- cast resolver/strtoupper inputs to string so a present-null config value
degrades gracefully instead of crashing
- list automations with config('app.pagination.default'), drop the perPage param
