[adamtheturtle]

Towards #3741. Depends on #3819.

Move the existing Flask, health-check and Docker deployment tests into server/tests/vws_mock_server_tests. The distinct import namespace lets core and server tests collect and type-check together. Load their shared fixture plugins from the existing root conftest while preserving its documentation collection.

Update the three CI partition paths, Docker disk-cleanup condition, source coverage, lint targets, consumer health-test path and development documentation. Keep server tests out of the image build context. Move the reusable processing-time helper into the installed contract suite and retain its old import as a compatibility forwarder.

The moved tests use the server package directly. Existing routing and health cases also verify that the legacy imports resolve to exactly the same applications and probe. The 100% coverage requirement is unchanged, and the moved test code remains included in coverage.

Validation:

• All 2,863 collected test IDs are preserved after mapping the moved paths.
• AST audit preserves 81 moved definitions apart from repository-root discovery and four compatibility identity checks; the shared timing helper is unchanged.
• All 64 server tests pass with the combined batch, including all six Docker deployment cases with two workers.
• The isolated installed-wheel consumer passes.
• All pre-commit and pre-push hooks, partition checks and type checkers pass; changed-file Pylint reports 10/10.

Shared API assertions remain in the contract package. The separate-repository extraction remains tracked by #3741.