a11y(frontend): make deposit and withdrawal wizards keyboard-complete and screen-reader safe

[arisu6804]

Problem

Multi-step financial forms can trap keyboard users, expose unlabeled controls, or announce validation and transaction state inconsistently.

Objective

Deliver a production-quality improvement to deposit and withdrawal forms that creates measurable value for correctness, security, reliability, performance, or maintainability.

Implementation scope

• Provide semantic labels, focus management, error association, and keyboard-complete controls.
• Announce step changes, balance/fee updates, and transaction outcomes without excessive repetition.
• Ensure dialogs and disabled states meet the application's accessibility baseline.

Acceptance criteria

• Every flow is operable without a pointer.
• Validation errors are programmatically associated with fields and announced.
• Automated accessibility checks pass with manual keyboard and screen-reader verification notes.

Required validation

• Component tests, axe-style checks, keyboard navigation tests, and focus/announcement assertions.
• Existing tests and CI remain passing.
• Add regression coverage for the original failure mode.
• Do not weaken, delete, or skip unrelated tests to obtain a green build.

PR quality bar

• Keep the PR focused on this issue and explain design tradeoffs.
• Include test evidence, compatibility impact, and migration or rollout notes where relevant.
• Avoid typo-only, documentation-only, cosmetic-only, or unrelated refactor submissions.

Out of scope

• Broad rewrites not required by the acceptance criteria.
• Changes to unrelated services, contracts, or user flows.