feat: implement portfolio UUID migration and v1 API finalization (BAT-006, BAT-001 re-verified)

Core Changes:
- Migrate portfolio_id from string to UUID in schema and repository layer
- Update portfolio CLI commands to use name+user combination for identification
- Update HTTP API to accept portfolio_id as UUID path parameter
- Implement portfolio ownership validation in repository queries

Requirements Completed (REQ-016 to REQ-019):
- REQ-016: portfolios table UUID schema migration with data migration script
- REQ-017: CLI portfolio commands with name+user identification
- REQ-018: HTTP API portfolio path parameters and v1 asset_id UUID returns
- REQ-019: Portfolio UUID baseline documentation updates

BAT-001 Re-verification:
- REQ-004~010 marked as Implemented after verification evidence validation
- All v1 API endpoints verified with comprehensive test coverage

Documentation Updates:
- Update data-model.md with portfolio UUID structure
- Update interface-contract.md with UUID path parameters
- Update runtime-flows.md with ownership-based resolution flows
- Update project-structure.md with database layer changes
- Add migration script for portfolio UUID transition

Testing:
- Add test_portfolio_uuid.py for migration validation
- Update test_cli.py and test_portfolio_ownership.py for ownership checks

docs/batches/bat-001_20260502_trex-basic-v1-api-contract/index.md

@@ -1,6 +1,6 @@
 # BAT-001 Index
 
-- Status: in-delivery
+- Status: release-candidate
 - Batch: BAT-001
 - Profile: standard
 - Created: 2026-05-02
@@ -61,7 +61,7 @@
 
 | Stage | File | Status |
 |-------|------|--------|
-| Planning | [planning.md](./planning.md) | draft |
-| Design | [design.md](./design.md) | draft |
-| Implementation | [implementation.md](./implementation.md) | draft |
-| Verification | [verification.md](./verification.md) | draft |
+| Planning | [planning.md](./planning.md) | confirmed |
+| Design | [design.md](./design.md) | confirmed |
+| Implementation | [implementation.md](./implementation.md) | completed |
+| Verification | [verification.md](./verification.md) | re-verified |