The strict source_type-availability validator from the prior commit
broke ~12 existing tests that register tables on the default test
instance (where `data_source.type` resolves to 'local' since no
instance.yaml is loaded).
The intent of the validator is to catch *explicit* misconfig:
`type=bigquery` instance + `source_type=keboola` payload with no
`data_source.keboola.*` block. The bootstrap workflow — admin sets up
a fresh instance and registers a few tables before pointing at a real
source — should not be gated here.
Loosen the check: when `get_data_source_type()` returns 'local' (the
fallback when no `data_source.type` is set), skip the rejection. The
explicit mismatch case still 422s because that path resolves
`configured_primary` to a real source type.
Also adds an autouse keboola_instance fixture to test_journey_sync_query.py
which exercises Keboola registrations through the full sync→query
flow — the fixture documents the test's data-source assumption rather
than relying on the bootstrap escape hatch.
