feat: move proxmox discovery/import/sync into a first-party plugin

plugins/proxmox/manifest.json

@@ -0,0 +1,27 @@
+{
+  "id": "proxmox",
+  "name": "Proxmox",
+  "version": "1.0.0",
+  "description": "Discover Proxmox VE guests over an existing SSH host, import them as Termix hosts, and keep them in sync.",
+  "author": { "name": "Termix" },
+  "license": "MIT",
+  "repository": "https://github.com/Termix-SSH/Termix",
+  "category": "Infrastructure",
+  "icon": "Server",
+  "engine": { "termix": ">=2.9.0", "api": "1" },
+  "capabilities": {
+    "backend": true,
+    "frontend": true,
+    "electron": true,
+    "platforms": ["linux", "win32", "darwin"]
+  },
+  "permissions": ["process:transport-owner"],
+  "contributes": {
+    "hostCapability": {
+      "key": "enableProxmox",
+      "labelKey": "hosts.proxmoxIntegration",
+      "editorTab": "proxmox"
+    }
+  },
+  "sidecars": []
+}