Define accessibility testing and quality-gate strategy

### Description

Define a pragmatic accessibility-testing approach for the web application, with automated checks supporting—not replacing—manual accessibility review.

### Action Items

- [ ] Refine scope around priority user journeys and applicable accessibility standard/target.
- [ ] Evaluate automated options, including axe integration with the future Playwright suite, linting, and CI reporting.
- [ ] Define manual testing expectations for keyboard navigation, focus management, semantics, screen-reader coverage, and color contrast.
- [ ] Identify false-positive management, ownership, and criteria for introducing required checks.
- [ ] Propose a phased rollout and a small initial baseline after the E2E strategy is approved.

### Additional Information

Status: Triage — refine standards, priority flows, tool choice, and ownership before implementation. Coordinate with #751 (E2E testing).

Start by reading issue #751 on the E2E strategy and reviewing the priority user journeys. Evaluate the proposed axe integration with the future Playwright suite, linting, CI reporting, and manual checks. Done means a phased accessibility-testing plan covering standards, ownership, false positives, required checks, and an initial baseline.

Written by the indexing model from the issue text.