feat: REQ-002/REQ-010 implementation — assets.tag_ids column + GET /v1/assets admin catalog (BAT-012)

- REQ-002 scope redefinition: portfolios.tag_ids → assets.tag_ids UUID[] column with GIN index
- REQ-010 augmentation: GET /v1/assets redesigned as admin catalog endpoint (admin-only, no token_type branching)
- Asset tagging infrastructure: tag_ids column, archived flag synthesis for inactive tags, list_assets N+1 optimization
- DB migration 20260521_0023: assets.tag_ids UUID[] NOT NULL DEFAULT '{}', idx_assets_tag_ids_gin
- Test suite: 17 new test cases for assets.tag_ids + GET /v1/assets AC-9~12 (362 tests total)
- Documentation: runtime flows, release baseline, batch verification all updated
- BAT-012 added to REL-001 Included Batch and marked release-candidate

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/releases/index.md

@@ -8,4 +8,4 @@
 
 | REL ID | Profile | Status | Included Batch | Date | Doc |
 | --- | --- | --- | --- | --- | --- |
-| REL-001 | app-service | draft | BAT-001~011 | 2026-05-21 | [rel-001](./rel-001_20260521_v1-api-full-surface.md) |
+| REL-001 | app-service | draft | BAT-001~012 | 2026-05-21 | [rel-001](./rel-001_20260521_v1-api-full-surface.md) |