Migrate context cutover audit read to FastAPI

[cbusillo]

Summary

• add native FastAPI GET /v1/product-profiles/{product}/context-cutover-audit
• preserve product_profile.read authz, DB-backed audit storage gating, context-boundary checks, and redacted audit response wrapper
• delete the exact legacy WSGI read branch and document the compatibility retirement

Validation

• uv run python -m unittest tests.test_http_app.FastApiProductContextCutoverAuditReadTests tests.test_service.LaunchplaneServiceTests.test_context_cutover_audit_route_is_retired_from_legacy_wsgi_app tests.test_product_profile_context_audit
• uv run python -m unittest
• uv run --extra dev mypy control_plane tests
• uv run --extra dev ruff check --diff .
• uv run --extra dev ruff check .
• uv run --extra dev ruff format --check control_plane/http_app.py control_plane/service.py tests/test_http_app.py tests/test_service.py
• uv run /Users/cbusillo/Developer/codex-skills/jetbrains-inspection/scripts/jb-inspect.py closeout --repo "/Users/cbusillo/Developer/launchplane" --scope changed_files

Notes

• full repo ruff format check still reports pre-existing unrelated formatting drift in 56 untouched files; changed files are formatted
• three read-only review agents returned green before push