Add integration tests for migration categories and execution

- Implemented MigrationCategoryTests to validate migration categorization for startup, release, seed, and data migrations.
- Added tests for edge cases, including null, empty, and whitespace migration names.
- Created StartupMigrationHostTests to verify the behavior of the migration host with real PostgreSQL instances using Testcontainers.
- Included tests for migration execution, schema creation, and handling of pending release migrations.
- Added SQL migration files for testing: creating a test table, adding a column, a release migration, and seeding data.

docs/implplan/SPRINT_329_docs_modules_signer.md

@@ -1,13 +1,15 @@
-# Sprint 329 - Documentation & Process · 200.S) Docs Modules Signer
-
-Active items only. Completed/historic work now resides in docs/implplan/archived/tasks.md (updated 2025-11-08).
-
-[Documentation & Process] 200.S) Docs Modules Signer
-Depends on: Sprint 100.A - Attestor, Sprint 110.A - AdvisoryAI, Sprint 120.A - AirGap, Sprint 130.A - Scanner, Sprint 140.A - Graph, Sprint 150.A - Orchestrator, Sprint 160.A - EvidenceLocker, Sprint 170.A - Notifier, Sprint 180.A - Cli, Sprint 190.A - Ops Deployment
-Summary: Documentation & Process focus on Docs Modules Signer).
-Task ID | State | Task description | Owners (Source)
---- | --- | --- | ---
-SIGNER-DOCS-0001 | DONE (2025-11-05) | Validate that `docs/modules/signer/README.md` captures the latest DSSE/fulcio updates. | Docs Guild (docs/modules/signer)
-SIGNER-OPS-0001 | TODO | Review signer runbooks/observability assets after next sprint demo. | Ops Guild (docs/modules/signer)
-SIGNER-ENG-0001 | DONE (2025-11-27) | Keep module milestones aligned with signer sprints under `/docs/implplan`. Added Sprint Readiness Tracker to `docs/modules/signer/implementation_plan.md` mapping 4 phases to 17+ sprint tasks across Sprints 100, 186, 401, 513, 514. Updated README with Sprint 0186/0401 completed tasks (SIGN-CORE-186-004/005, SIGN-TEST-186-006, SIGN-VEX-401-018). | Module Team (docs/modules/signer)
-SIGNER-OPS-0001 | TODO | Sync outcomes back to ../.. | Ops Guild (docs/modules/signer)
+# Sprint 329 - Documentation & Process · 200.S) Docs Modules Signer
+
+> **BLOCKED Tasks:** Before working on BLOCKED tasks, review [BLOCKED_DEPENDENCY_TREE.md](./BLOCKED_DEPENDENCY_TREE.md) for root blockers and dependencies.
+
+Active items only. Completed/historic work now resides in docs/implplan/archived/tasks.md (updated 2025-11-08).
+
+[Documentation & Process] 200.S) Docs Modules Signer
+Depends on: Sprint 100.A - Attestor, Sprint 110.A - AdvisoryAI, Sprint 120.A - AirGap, Sprint 130.A - Scanner, Sprint 140.A - Graph, Sprint 150.A - Orchestrator, Sprint 160.A - EvidenceLocker, Sprint 170.A - Notifier, Sprint 180.A - Cli, Sprint 190.A - Ops Deployment
+Summary: Documentation & Process focus on Docs Modules Signer).
+Task ID | State | Task description | Owners (Source)
+--- | --- | --- | ---
+SIGNER-DOCS-0001 | DONE (2025-11-05) | Validate that `docs/modules/signer/README.md` captures the latest DSSE/fulcio updates. | Docs Guild (docs/modules/signer)
+SIGNER-OPS-0001 | TODO | Review signer runbooks/observability assets after next sprint demo. | Ops Guild (docs/modules/signer)
+SIGNER-ENG-0001 | DONE (2025-11-27) | Keep module milestones aligned with signer sprints under `/docs/implplan`. Added Sprint Readiness Tracker to `docs/modules/signer/implementation_plan.md` mapping 4 phases to 17+ sprint tasks across Sprints 100, 186, 401, 513, 514. Updated README with Sprint 0186/0401 completed tasks (SIGN-CORE-186-004/005, SIGN-TEST-186-006, SIGN-VEX-401-018). | Module Team (docs/modules/signer)
+SIGNER-OPS-0001 | TODO | Sync outcomes back to ../.. | Ops Guild (docs/modules/signer)