Add felhom-hub: multi-customer dashboard service

- Hub service receives reports from customer controllers
- SQLite store with 90-day retention and auto-prune
- REST API: POST /api/v1/report, GET /api/v1/customers
- Dark theme dashboard with status overview table
- Customer detail page with system, storage, containers, backup, health
- Bearer token auth for report ingest, bcrypt auth for dashboard
- K8s manifest for felhom-system namespace (Deployment, Service, Ingress, PVC)
- Dockerfile with multi-stage build

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

hub/configs/hub.yaml.example

@@ -0,0 +1,32 @@
+# =============================================================================
+# Felhom Hub Configuration
+# =============================================================================
+# Location: /etc/felhom-hub/hub.yaml (or mount as ConfigMap in k8s)
+#
+# The hub receives health reports from customer controllers and serves
+# a multi-customer overview dashboard for the operator.
+# =============================================================================
+
+# --- Authentication ---
+auth:
+  # Bcrypt hash for dashboard login (Viktor only)
+  password_hash: ""
+
+# --- API ---
+api:
+  # Bearer token required for report ingest (POST /api/v1/report)
+  report_api_key: ""
+
+# --- Data retention ---
+retention:
+  max_days: 90               # Keep 90 days of report history
+  prune_schedule: "04:30"    # Daily prune time (Europe/Budapest)
+
+# --- Alerting thresholds ---
+alerting:
+  stale_threshold: "30m"     # Customer considered stale if no report for this duration
+
+# --- Server ---
+server:
+  listen: ":8080"
+  data_dir: "/data"          # SQLite database location