Re-enable the disabled tests that already pass

[rbardaji]

Problem

tests/ holds 17 files parked as *.py.disabled. Four of them pass unchanged
against the current code — 48 test cases that are written, working, and simply
switched off.

File	Cases	Covers
test_pelican_routes.py.disabled	20	Pelican routes
test_update_kafka_datasource.py.disabled	14	Kafka datasource updates
test_search_routes_get.py.disabled	8	routes/search_routes/get.py
test_metrics_organization.py.disabled	6	Organization metrics

This is not only lost tests, it is lost coverage on code that ships.
api/routes/search_routes/get.py currently sits at 0.00% coverage, and the
search router is mounted unconditionally — it is present in every deployment,
whatever the catalog backend. Its test file exists and passes; it is just not
being collected.

Two other low-coverage modules line up with disabled files the same way:
search_datasource_route at 12% and register_routes/post_general_dataset.py
at 26.5%.

Note on test_pelican_routes

Both tests/test_pelican_routes.py and tests/test_pelican_routes.py.disabled
exist. The two need comparing before the disabled one is restored, so the suite
does not end up with duplicate or conflicting cases.

Proposal

Rename the four files back to .py and let CI run them. No test code needs
writing.

Out of scope

The other 13 disabled files fail and need real work. They should be triaged
separately, grouped by area (Kafka, organizations, search, MinIO). Their
failures are currently hard to read because Pydantic V1-style deprecation
warnings from api/models/service_request_model.py and
api/models/update_service_model.py flood the output.

Acceptance criteria

• The four files are collected and pass in CI.
• api/routes/search_routes/get.py is no longer at 0% coverage.
• The duplicate test_pelican_routes situation is resolved, with only one
  copy left.
• The remaining 13 files are untouched and still disabled.