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>

.env.example

@@ -0,0 +1,21 @@
+# Copy to .env and fill in. Never commit the real .env (see .gitignore).
+
+# Proxmox API token — see docs in the "Provision read-only Proxmox API token" issue
+# for how this was created (dedicated monitor@pve user, PVEAuditor role).
+PROXMOX_TOKEN_ID=monitor@pve!dashboard
+PROXMOX_TOKEN_SECRET=
+
+# Session cookie signing key — generate with: openssl rand -hex 32
+SESSION_SECRET=
+
+# Seeded on first boot only; change the password after first login isn't
+# implemented yet (see backlog), so pick a real one now.
+ADMIN_USERNAME=admin
+ADMIN_PASSWORD=
+
+# local | oidc (oidc not implemented yet, see issue #12)
+AUTH_MODE=local
+
+PORT=3000
+POLL_INTERVAL_SECONDS=30
+SNAPSHOT_RETENTION_HOURS=24