feat(doi): Repository DoI automated gate and dashboard integration (CUST-WP-0024)

Implements the 14-criterion DoI checklist as a runnable gate with API,
MCP tools, CLI script, and dashboard integration.

Core components:
- api/doi_engine.py — async engine evaluating all 14 criteria (asyncio.to_thread
  for non-blocking HTTP self-calls), shared by API and CLI
- api/schemas/doi.py — DoICriterion, DoIReport, DoISummaryEntry schemas
- api/routers/repos.py — GET /repos/{slug}/doi + GET /repos/doi/summary
- scripts/check_doi.py — CLI: make check-doi REPO=<slug> / check-doi-all
- mcp_server/server.py — check_repo_doi(), get_doi_summary() tools

Dashboard (repos.md):
- DoI tier badge per repo (None/Core/Standard/Full) colour-coded red→green
- Domain block shows lowest DoI tier across its repos
- DoI KPI card in summary row
- DoI filter in All Repos Table
- Link to Repository DoI policy page

Also fixes: TPSC snapshots 500 error (missing nested selectinload for
catalog_entry relationship in list_snapshots endpoint).

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Makefile

@@ -183,6 +183,17 @@ ingest-capabilities-all:
 	uv run python scripts/ingest_capabilities.py --all \
 		$(if $(DRY_RUN),--dry-run)
 
+## Check Repository Definition of Integrated (DoI) criteria for a repo.
+## Usage: make check-doi REPO=llm-connect
+## Or:    make check-doi-all
+## Add JSON=1 for machine-readable output.
+check-doi:
+	@test -n "$(REPO)" || (echo "ERROR: REPO is required."; exit 1)
+	uv run python scripts/check_doi.py --repo "$(REPO)" $(if $(JSON),--json)
+
+check-doi-all:
+	uv run python scripts/check_doi.py --all $(if $(JSON),--json)
+
 ## Ingest tpsc.yaml service declarations from a repo into the TPSC catalog.
 ## Usage: make ingest-tpsc REPO=llm-connect
 ## Or:    make ingest-tpsc-all