Scaffold homelab-monitor: Fastify API + React dashboard + CI

Vertical slice for Phase 1 (v1-dashboard milestone): Proxmox collector,
SQLite storage, local auth, and a dashboard UI showing host/container
status cards. Config-driven collector registry so future data sources
(SSH-based hosts, Zabbix, network discovery) plug in without rewiring.

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

config/hosts.yaml

@@ -0,0 +1,5 @@
+# Declares what the dashboard monitors. No secrets here — credentials come from
+# environment variables (see .env.example) so this file can be committed safely.
+proxmox:
+  host: 192.168.1.144
+  node: pve