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").
Move the lifecycle service, Celery task bodies, and mark_failed coverage out of
DB-faking unit tests and into integration tests against a real Postgres, faking
only true externals (broker, object store, TTS, ffmpeg, billing, LLM). Add HTTP
slices for cancel, voices, scoping, and public-chat streaming. The unit tier is
now fake-free pure logic with no session doubles.
