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/master-cms-module/audit.md

@@ -1,5 +1,17 @@
 # Audit Log — Master CMS Module
 
+## Documentation Audit & Correction — Post-`local-dev-master-slave-setup` Follow-Up Fixes
+
+**Timestamp**: 2026-07-04T00:00:00Z
+
+**User Input**: "ja zet het erbij en check alles ook tegenover de aidlc documentatie" (in response to a request to also add README docs for a new master-controlled availability lock, and to cross-check everything against the AI-DLC documentation)
+
+**AI Response**: "Dispatched an Explore subagent to compare the functional-design docs here against the actual as-built code, given a string of same-day fixes (in the local-dev-master-slave-setup feature's session) that changed real master/slave protocol behavior: Inactive now releases the gate instead of doing nothing, VerifyIntegrityAsync now re-pushes status (not just URL-verification) and IntegrityCheckBackgroundService runs once on startup, a new slave-pull mechanism (SlaveStatusController + MasterStatusPollingBackgroundService + fail-open via MasterRegistration.LastPolledAt) was added, and PersistentAvailabilityService now merges/enforces the master gate (IsMasterControlled, MasterControlledAvailabilityException, 409 Conflict) instead of ignoring it. Found and corrected multiple actively-contradicted statements: construction/master-backend/functional-design/{business-rules,business-logic-model,domain-entities}.md (Inactive-transition push behavior, SlaveContactSuccess semantics, VerifyIntegrityAsync flow, added new Slave Pull and Master-Controlled-Lock rule sections); construction/slave-availability-extension/functional-design/{business-rules,business-logic-model,domain-entities}.md (master-gate cache no longer 'no expiry', added LastPolledAt field, added Rule Sets 5-6 and Flows 5-6 for the pull/fail-open and lock mechanisms); inception/application-design/application-design.md (Inactive/fail-open constraint rows). Also fixed one long-standing (pre-2026-07-04, unrelated to today) inaccuracy found in passing: slave-availability-extension/domain-entities.md claimed MasterRegistration.ApiKey is stored plain-text, but the code (MasterAvailabilityService using IMasterApiKeyProtector) actually encrypts it. Separately flagged (added superseded-warning banners rather than rewriting) a much larger, pre-existing divergence in inception/application-design/{services,components,component-methods}.md: these inception-stage docs describe an entirely different pull-based design (static cache + MasterModuleOptions.CacheMinutes + /api/internal/master/* routes) that construction never actually built — this predates today's session and is a separate, bigger gap than what today's fixes caused; not fully rewritten, just clearly marked as historical/superseded pending a dedicated pass. Also added a code-summary.md addendum for master-backend listing the new SlaveStatusController/methods. Re-ran the full backend suite after all doc edits (docs-only + two appsettings.json additions) to confirm nothing was inadvertently broken: 219/219 pass."
+
+**Context**: This is a documentation-only audit and correction pass — no application code was changed (only aidlc-docs/*.md files and two appsettings.json files that added a previously-Development-only MasterPolling config section to the base/production configs for consistency, functionally a no-op since the C# options class already had matching defaults).
+
+---
+
 ## Build and Test Stage — Approved
 
 **Timestamp**: 2026-07-01T00:10:00Z