refactor: slim Database to control-plane store (#599 PR2/3)

## Summary
PR 2 of 3 for #599. The global Database becomes a control-plane store only
(auth/api-keys/audit/interactive-sessions/token-usage); v2 domain data already
lives per-workspace via core/workspace.py.

- database.py: 863 -> 285 lines. Dropped every dropped-table method + the
  *_repository compat properties. Kept connection plumbing and the live
  token + audit delegations.
- Deleted 16 v1 repositories + codeframe/enforcement/ (reachable only via the
  removed task_repository) + codeframe/git/workflow_manager.py (never
  instantiated; only re-exported) and emptied git/__init__.py.
- Trimmed dead fixtures from integration/api/ui conftests and reconciled
  the root collect_ignore. Removed ~46 v1 tests of the deleted code.

## Validation
- Tests: pytest -m v2 green (2824 passed); Backend + Frontend CI green
- Lint/Type: ruff + mypy clean (181 files); CI Code Quality green
- Collect: pytest --collect-only clean (3437); zero tracked .py reference any removed symbol
- Boot: TestClient /health -> 200; cf --help / cf status
- Runtime introspection: Database control-plane surface verified
  (keep-set repos wired, dropped attrs/methods absent, audit round-trip works)
- Cross-family review: codex (0 findings) + CodeRabbit (Review completed)
- claude-bot advisory: 3 in-scope fixes landed (ef64783), 3 pre-existing
  deferred items documented; bot follow-up confirms no blocking findings
- Demo: all 11 acceptance criteria mapped to outcome evidence

Deferred:
- persistence -> platform_store rename + CLAUDE.md repo-structure -> PR3
- pre-existing thread-safety / INSERT duplication / async PRAGMA repetition
  in token_repository.py / audit_repository.py / database.py async setup
  belong in a separate "harden surviving repos" PR

Part of #599 (PR2 of 3 -- does not close).

Author: frankbria