feat: add monitoring dashboard (Prometheus + Grafana + Umami + Admin)

Phase 1: Infrastructure
- Add docker/prometheus/prometheus.yml with scrape configs for all services
- Add docker/grafana/provisioning for auto-configured datasources
- Add docker/grafana/dashboards (system-overview, backends-docker)
- Update docker-compose.macmini.yml with monitoring services:
  - prometheus, grafana, node-exporter, cadvisor
  - postgres-exporter, redis-exporter, umami
- Add grafana.mana.how and analytics.mana.how to Caddyfile

Phase 2: Backend Metrics
- Create packages/shared-nestjs-metrics with:
  - MetricsModule (auto /metrics endpoint)
  - MetricsService (Counter, Histogram, Gauge helpers)
  - MetricsMiddleware (auto HTTP request tracking)

Phase 3: Umami Web Analytics
- Add Umami tracking scripts to all landing pages
- Add Umami tracking scripts to all web apps
- Create scripts/mac-mini/setup-umami-db.sh

Phase 4: Admin Dashboard (ManaCore Web)
- Add admin routes: /admin, /admin/users, /admin/system
- Create StatCard, QuickLinks, UserTable components
- Add Admin link to navigation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.env.macmini.example

@@ -31,3 +31,13 @@ SUPABASE_SERVICE_ROLE_KEY=
 # ============================================
 AZURE_OPENAI_ENDPOINT=https://your-resource.openai.azure.com/
 AZURE_OPENAI_API_KEY=your-api-key-here
+
+# ============================================
+# Monitoring (Grafana)
+# ============================================
+GRAFANA_PASSWORD=your-grafana-admin-password
+
+# ============================================
+# Web Analytics (Umami)
+# ============================================
+UMAMI_APP_SECRET=your-umami-secret-here