id: BT-001C
title: Shared Historical Fixture/Test Provider Cleanup
status: done
priority: P2
effort: S
depends_on:
  - BT-001A
  - BT-003A
tags:
  - backtesting
  - test-infra
summary: Deterministic historical fixture logic for browser-tested backtest UIs is now centralized behind a shared fixture source used by both `/backtests` and `/event-comparison`.
completed_notes:
  - Added `app/services/backtesting/fixture_source.py` with shared seeded GLD fixture history and explicit exact-vs-bounded window policies.
  - Updated `app/services/backtesting/ui_service.py` so the `/backtests` page uses the shared fixture source in exact-window mode and still fails closed outside the seeded BT-001A range.
  - Updated `app/services/event_comparison_ui.py` so the `/event-comparison` page uses the same shared fixture source in bounded-window mode for preset subranges inside the seeded BT-003A fixture window.
  - Added focused regression coverage in `tests/test_backtesting_fixture_source.py` proving the shared source enforces exact and bounded policies explicitly and that both page services use the centralized fixture source.
  - During this implementation loop, local Docker validation stayed green on the affected historical routes: `/health` returned OK and `tests/test_e2e_playwright.py` passed against the Docker-served app.