feat: QA 205, 206, 207 and 208

[A6dulmalik]

Summary

• What changed and why?

Related Issues

• Closes QA-205: Add legacy backend module smoke gate grouped by debt bucket #802
• Closes QA-206: Validate contributor bootstrap and setup scripts on a clean checkout #803
• Closes QA-207: Add example env validation tests for frontend backend and Soroban surfaces #804
• Closes QA-208: Add projection migration compatibility tests #805

Change Type

• Bug fix
• Feature
• Refactor
• Docs
• CI/Build
• Breaking change

How To Test

• npm run lint --prefix backend
• npm run typecheck --prefix backend
• npm run test --prefix backend
• npm run lint --prefix frontend
• npm run typecheck --prefix frontend
• npm run build --prefix frontend

Screenshots / Recordings (if UI)

Checklist

• I read CONTRIBUTING.md
• I added or updated tests where relevant
• I updated docs where relevant
• I kept the scope focused

Wave Contributor Checklist (Stellar Wave issues only)

• PR title follows [W5][TRACK][SIZE] description convention
• All acceptance criteria from the linked issue are addressed
• Validation evidence included (commands run + outputs)
• No cross-track changes without explicit note
• Architectural changes reflected in docs or ADR (if applicable)

[drips-wave]

@A6dulmalik Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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[kike-alt]

Replaced by updated branch