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>

app/schemas/v1.py

@@ -237,6 +237,7 @@ class AssetCatalogResponse(BaseModel):
     markets: list[str]
     display_name: str | None = None
     status: str
+    tag_ids: list[TagRefItem] = Field(default_factory=list)
     created_at: datetime | None = None
     updated_at: datetime | None = None