feat(git-sync): GitSyncModule orchestrator + config + listener (Phase A.4b/B)

Control plane wiring (plan §5-§11):
- PageService create/update/movePage now honor provenance actor 'git-sync'
  (stamp lastUpdatedSource='git-sync'), closing the A.4a gap.
- EnvironmentService: GIT_SYNC_ENABLED / DATA_DIR / REMOTE_TEMPLATE /
  POLL_INTERVAL_MS / DEBOUNCE_MS / SERVICE_USER_ID (required-if-enabled) /
  SSH_KEY_PATH + validation.
- VaultRegistryService: per-space vault path + cached VaultGit.
- GitSyncOrchestrator: per-space Redis leader-lock (SET NX PX + CAS-Lua release,
  randomUUID instanceId) + in-process mutex; runOnce drives the vendored engine
  PULL (readExisting->computePullActions->applyPullActions) then PUSH (runPush)
  with the bound native GitSyncClient + VaultGit; @Interval poll-safety gated on
  GIT_SYNC_ENABLED; imports plain ScheduleModule (TelemetryModule owns forRoot).
- PageChangeListener: @OnEvent PAGE_* -> per-space debounce -> runOnce, with a
  best-effort lastUpdatedSource==='git-sync' loop-guard.
- GitSyncController: admin POST /api/git-sync/trigger + GET /status (ops/e2e).
- GitSyncModule registered in app.module. Enabled-space enumeration uses
  settings.gitSync.enabled, falling back to all live spaces until Phase C writes
  the flag (master gate = GIT_SYNC_ENABLED).

tsc clean; 713 tests/71 suites pass; dev server hot-reloaded the module (route
live, DI graph boots). Live pull/push round-trip verified next.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/server/src/app.module.ts

@@ -28,6 +28,7 @@ import { ClsModule } from 'nestjs-cls';
 import { NoopAuditModule } from './integrations/audit/audit.module';
 import { ThrottleModule } from './integrations/throttle/throttle.module';
 import { McpModule } from './integrations/mcp/mcp.module';
+import { GitSyncModule } from './integrations/git-sync/git-sync.module';
 import { AiModule } from './integrations/ai/ai.module';
 import { AiChatModule } from './core/ai-chat/ai-chat.module';
 
@@ -89,6 +90,7 @@ try {
     TelemetryModule,
     ThrottleModule,
     McpModule,
+    GitSyncModule,
     AiModule,
     AiChatModule,
     ...enterpriseModules,