Introduces the Municipalities namespace with domain entity, in-memory
repository, and REST API. Extends the workspace shell with a live panel.

Backend:
- MunicipalityProfile record (ILegacyLinkedRecord) — participates in
  Story 1.8 nightly link integrity check automatically
- InMemoryMunicipalityProfileRepository — validates JCode before save
  (AC #4), resolves legacy jurisdiction for combined views (AC #2)
- POST/GET/PUT /api/municipalities/profiles — ClientServicesAccess policy;
  audit-logged creates and updates (AC #3)

Frontend:
- municipalityContracts.ts — typed fetch helpers, MunicipalityValidationError
- MunicipalityProfilePanel — table with combined legacy+extension data,
  modal create form with JCode validation error display
- WorkspaceShell — municipalities nav now renders the panel

Tests: 16 backend + 9 frontend (133 server / 36 client total, 0 failures)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>