feat: deploy StepFi-Web to Vercel with CI

[EmeditWeb]

Problem

StepFi-Web is only running locally. It needs to be
deployed to a public URL so sponsors and vendors
can access it.

What To Build

1. Add vercel.json to the repo root:
   {
   'framework': 'vite',
   'buildCommand': 'npm run build',
   'outputDirectory': 'dist',
   'rewrites': [{ 'source': '/(.*)', 'destination': '/index.html' }]
   }

2. Add build step to CI workflow

3. Update README with live URL once deployed

4. Add VITE_API_BASE_URL environment variable
   in Vercel project settings pointing to:
   https://stepfi-api.onrender.com/api/v1

Files To Touch

• vercel.json (new)
• .github/workflows/ci.yml
• README.md

Acceptance Criteria

• App builds on Vercel without errors
• All routes work (SPA routing via rewrite)
• API base URL configured via env var
• Live URL added to README

Mandatory Checks Before PR

• Vercel build passes
• All routes accessible on live URL
• PR references this issue

[Mmesolove]

Hi maintainer,I have read the description and I can resolve this issue, please kindly assign to me.

[EneGab]

Hi maintainer! i can work on this, please assign me the task

[grantfox-oss]

🦊 GrantFox — @EneGab 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 #15)
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!

@EneGab's PR #33 was approved and merged by @EmeditWeb.

🏆 @EneGab: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (48 total points). Track your full progress on GrantFox.

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