Initial implementation: host lifecycle + PXE + admin dashboard

Go service for Proxmox homelab cluster provisioning. Handles PXE boot,
Proxmox autoinstall (answer file generation), cluster join via SSH,
and Infrastructure API registration.

- Host state machine (registered → pxe_ready → installing → ready)
- dnsmasq supervisor with MAC-based allowlist
- iPXE script and Proxmox answer file generation
- First-boot phone-home → cluster join → infra registration
- Operation locking with expiry (409 on conflict)
- SSE event hub for real-time dashboard updates
- Admin dashboard (host grid, detail, registration form)
- Config-driven server types with hot-reload
- Docker deployment (multi-stage fat image)

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

deploy/provisioning.example.yaml

@@ -0,0 +1,40 @@
+server:
+  bind: "0.0.0.0:8080"
+  public_url: "http://192.168.1.100:8080"
+
+database:
+  path: "./data/provisioning.db"
+
+pxe:
+  enabled: true
+  interface: "eth0"
+  subnet: "192.168.1.0/24"
+  runtime_dir: "./data/pxe"
+  tftp_root: "./data/tftp"
+  dnsmasq_bin: "/usr/sbin/dnsmasq"
+
+images:
+  dir: "./data/images"
+
+proxmox:
+  existing_node: "192.168.1.10"
+  cluster_name: "homelab"
+  join_fingerprint: "AA:BB:CC:DD:EE:FF:00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF:00:11:22:33:44:55:66:77:88:99"
+
+credentials:
+  ssh_private_key_path: "/etc/provisioning/keys/id_ed25519"
+  ssh_public_key: "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAEXAMPLE provisioning@homelab"
+  root_password_hash: "$6$rounds=5000$randomsalt$hashedpasswordhere"
+
+infrastructure:
+  base_url: "http://192.168.1.50:3000"
+  room_id: 1
+  server_type_map:
+    minisforum-ms-01: 1
+    minisforum-um790: 2
+  timeout_seconds: 10
+
+locks:
+  ttl_minutes: 60
+
+server_types_path: "./server-types.yaml"