feat: add GitHub Actions CI for StepFi-Web

[EmeditWeb]

Problem

StepFi-Web has no CI pipeline. PRs can break
the build without anyone knowing until it is
deployed.

What To Build

Create .github/workflows/ci.yml:

Runs on every PR to main:

1. Checkout code
2. Setup Node 20
3. npm install
4. npm run build
5. npm run lint (if configured)

Add status badge to README.md.

Files To Touch

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

Acceptance Criteria

• CI runs on every PR
• Build failure blocks merge
• Status badge shows in README
• Runs in under 3 minutes

Mandatory Checks Before PR

• The CI workflow itself passes on first run
• PR references this issue

[Mmesolove]

Hi Maintainer, I’ve gone through the issue details and I’m confident I can work on and resolve it. Kindly assign this issue to me. I’ll be glad to contribute. Thanks!

[Spagero763]

i can work on this issue

[Iwayemi-Kehinde]

I would like to work on this issue as I have reviewed the scope, I should have a PR Ready in 50 minutes.

[OG-wura]

i would love to work on this