Consolidate GovTool into a single monorepo

## Outcome

GovTool is developed, tested, versioned, and released from one repository with clear package and service boundaries.

## Scope

- Approve the target repository topology and package boundaries
- Move shared contracts, backend, frontend, utilities, tests, and documentation
- Consolidate CI, dependency management, build, release, and deployment workflows
- Document migration, validation, rollback, and archive procedures

## Acceptance criteria

- [ ] Scope is decomposed into independently deliverable child issues.
- [ ] Architecture and API decisions are linked from this issue.
- [ ] Test, documentation, observability, rollout, and failure behavior are defined where applicable.
- [ ] Epic exit criteria are verified before closure.

## Planning note

This is a 2026 GovTool revamp work item. Its child features and tasks should be added as the scope is refined.