feat: move proxmox node stats and collectors into the proxmox plugin

plugins/proxmox/src/backend/plugin-ctx.ts

@@ -0,0 +1,13 @@
+import type { PluginContext } from "@termix/plugin-sdk/backend";
+
+let current: PluginContext | null = null;
+
+/** Set in activate, cleared on deactivate. */
+export function setPluginCtx(ctx: PluginContext | null): void {
+  current = ctx;
+}
+
+export function pluginCtx(): PluginContext {
+  if (!current) throw new Error("The plugin is not active");
+  return current;
+}