Apply the same rename to surfsense_backend/tests: workspace_id fields/vars,
Workspace* classes/schemas, table name searchspaces -> workspaces in raw SQL,
and the API URL spellings -> /workspaces. Preserves the carve-out wire literals
tests assert (Celery task names, OTel key "search_space.id").
Cover the cron + IANA timezone + UTC normalization contract for the
schedule trigger: next-match strictly-after, DST offset shift across
spring-forward, malformed cron / unknown timezone rejection, and the
ScheduleTriggerParams Pydantic gate that surfaces InvalidCronError as
ValidationError at the API boundary.
8 tests, pure unit (no DB, no mocks).
