feat: unify wallet transaction lifecycle (#55 #56 #66)

[barry01-hash]

Closes #83

Summary

Closes #[issue number]

Briefly describe what this PR does in 2-3 sentences.

This repo is for the React web app only

This app targets sponsors, vendors, and mentors.
It does NOT serve learners. Learner features
belong in StepFi-App.

Before submitting, confirm your changes belong here:

• My changes are inside src/
• I have NOT added Rust, Soroban, or
  contract code
• I have NOT added React Native or
  Expo-specific code
• I have NOT hardcoded hex color values
  (use Tailwind classes or constants/colors.ts)
• All icons are from lucide-react only
• No API calls made directly in page files
  (use services/ layer only)

Type of change

• Bug fix
• New page or component
• Service layer addition
• Styling or responsive fix
• Accessibility improvement
• Performance improvement

Testing

• npm run build passes with zero errors
• npm run lint passes with zero errors
• Loading, error, and empty states handled
• Page tested on mobile viewport (375px)
• No console errors in browser

Context files reviewed

• context/architecture-context.md
• context/code-standards.md
• context/progress-tracker.md updated

Mandatory before requesting review

Running these must all exit 0:
npm run lint
npm test
npm run build

If either fails, fix it before opening this PR.
PRs that reduce the test count will be rejected.
PRs with failing CI will be closed without review.

[barry01-hash]

Please merge

[EmeditWeb]

please fix CI issues

[EmeditWeb]

Review verdict: ✅ APPROVE

Nice unification — this net-removes ~140 lines while centralizing the transaction lifecycle in a dedicated transaction.service.ts with tests. Verified locally: build passes, lint is clean, tests pass (24). Standards check is clean: no hardcoded hex colors, no API calls in page components (pages delegate to the service/hooks), and no any in the new service.

The red CI appears stale (this branch is green locally). Please re-run it.

One suggestion (non-blocking): since this touches the signing→submit path, a quick manual smoke test of an end-to-end vouch/sponsor transaction in the browser before merge would be worthwhile — the automated tests cover the units but not the full wallet round-trip.

[barry01-hash]

Please merge

[EmeditWeb]

repush to trigger the CI workflow