Completes local-dev-master-slave-setup: dual-instance frontend tooling, module-capability gating, and master/slave protocol self-healing fixes

Frontend (Unit 2 completion): dual dev-server tooling (pnpm dev:slave,
pnpm dev:all), per-instance browser tab titles, and a backend
capability check (SystemController + useSystemCapabilities +
ModuleGuard) so a Master-only page is hidden on a slave instance
instead of assuming every backend has every module.

Master/slave protocol fixes surfaced by actually running master and
slave side by side locally:
- Deactivating a CMS instance (Inactive) now releases the slave's
  master gate instead of leaving it stuck on its last pushed status.
- The periodic integrity check now also re-pushes status to every
  reachable slave (previously URL-verification only) and runs once
  immediately on startup.
- Added the originally-specified (but never implemented) slave-pull
  path: a slave now periodically polls its own status from the master
  (GET /api/v1/SlaveStatus) and fails open to Available if the master
  is unreachable for too long, complementing the existing push.
- The slave's own Settings page can no longer "successfully" change
  local availability while the master controls it; it's now locked
  with an explanatory banner and the backend rejects the write with
  409 instead of silently no-op'ing it.
- CMS instance status badges now match the dashboard's color/icon
  styling instead of a plain grey badge.

Also corrected the master-cms-module design docs to match this
as-built behavior, and flagged (without a full rewrite) a larger,
pre-existing divergence between its inception-stage application
design and what construction actually built.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

aidlc-docs/features/local-dev-master-slave-setup/aidlc-state.md

@@ -5,7 +5,7 @@
 - **Feature Slug**: local-dev-master-slave-setup
 - **Project Type**: Brownfield
 - **Start Date**: 2026-07-02T00:00:00Z
-- **Current Stage**: CONSTRUCTION - Unit 2 (Frontend dual-instance tooling & runbook) - Code Generation
+- **Current Stage**: OPERATIONS - Placeholder (feature complete)
 - **Branch**: unknown
 
 ## Workspace State
@@ -42,5 +42,5 @@
 
 ### 🟢 CONSTRUCTION PHASE
 - [x] Unit 1 (Backend dual-instance hosting) — Code Generation complete (`construction/unit-1-backend-dual-instance-hosting/code/summary.md`); build + full test suite verified green; manual module-discovery check confirms slave excludes Master
-- [ ] Unit 2 (Frontend dual-instance tooling & runbook) — In Progress
-- [ ] Build and Test — Not started
+- [x] Unit 2 (Frontend dual-instance tooling & runbook) — Code Generation complete (`construction/unit-2-frontend-dual-instance-tooling/code/summary.md`)
+- [x] Build and Test — Complete (`construction/build-and-test/build-and-test-summary.md`); build succeeds, 193/193 automated tests pass, module isolation verified manually, end-to-end connection test documented as a manual follow-up (no local SQL Server available in this session)