[souravC01]

Summary

• make backend impact analysis the authoritative source for continuity-risk projections
• synchronize a role's complete holder set in one atomic backend transaction
• harden projection consistency, concurrent reads, async selection behavior, and request-contract coverage

Why

The editor previously duplicated a smaller subset of continuity rules in the browser, which could disagree with the impact engine. Role-holder edits were also applied member by member, allowing partial updates if one request failed.

Validation

• backend: full Maven test suite — 31 tests passed
• frontend: 13 tests passed
• frontend lint passed
• frontend production build passed
• git diff --check passed

Risk and rollback

The main risk is compatibility at the draft continuity and role-assignment API boundaries. Unit, integration, concurrency, and frontend request-contract tests cover those boundaries. Rollback is a normal revert of this PR; there are no database migrations.