core: implement accessibility (WCAG 2.1 AA compliance)

[EmeditWeb]

Problem

The web app has no accessibility considerations.
Screen readers cannot navigate. Keyboard navigation
does not work.

What To Build

1. Semantic HTML audit
2. Keyboard navigation (tab order, focus styles)
3. Screen reader support (aria attributes)
4. Color contrast compliance (4.5:1 ratio)
5. Form accessibility (labels, error messages)
6. axe-core CI integration

Files To Touch

All component files in src/components/
All page files in src/pages/

Acceptance Criteria

• axe-core reports zero violations
• Keyboard navigation works on all pages
• Screen reader can complete main flows
• Color contrast meets WCAG AA
• npm run build passes

Mandatory Checks Before PR

• npm run build passes
• axe-core scan passes
• PR references this issue

[Adeyemi-cmd]

i would love to work on this

[OG-wura]

can I work on this please

[onajidavid87-web]

i would love to work on this issue

[grantfox-oss]

🦊 GrantFox — @onajidavid87-web has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #30)
2. Your PR will be reviewed by the StepFi-app maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@onajidavid87-web's PR #45 was approved and merged by @EmeditWeb.

🏆 @onajidavid87-web: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (83 total points). Track your full progress on GrantFox.

👏 Great work, @onajidavid87-web! Keep contributing to StepFi-app.