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

plugins/proxmox/backend/index.mjs

@@ -0,0 +1,63 @@
+/**
+ * Proxmox discovery/import/sync - first-party, in-process plugin.
+ *
+ * This plugin runs on the main thread rather than in a worker for the same
+ * reason ai does (see src/backend/plugins/first-party.ts): it writes
+ * directly across hosts through the host repository, resolves and connects
+ * to hosts over the shared SSH pool via resolveHostById and
+ * createJumpHostChain, verifies host keys via SSHHostKeyVerifier, and
+ * streams its discovery progress as server-sent events. None of that fits
+ * the worker ctx -- ctx.hosts is a 13-field read-only view with no write
+ * methods, and ctx.http.route replies with a single postMessage value
+ * rather than a stream.
+ *
+ * Like ai, this plugin does not own a live transport (no WebSocket server,
+ * no dedicated port), so it registers its Express router with the
+ * always-mounted /proxmox dispatcher in
+ * src/backend/database/routes/proxmox-dispatch.ts instead of getting its
+ * own port.
+ *
+ * routes.ts is what used to be src/backend/database/routes/proxmox.ts,
+ * moved here with its sibling modules (proxmox-import-auth.ts,
+ * proxmox-jump-hosts.ts) and rewritten from `export default router` into
+ * startProxmoxService()/stopProxmoxService(), called from
+ * activate()/deactivate() below. Those two functions also start and stop
+ * the background auto-sync interval that used to run at module scope in
+ * proxmox.ts -- keeping it there would mean it fires even when this plugin
+ * is disabled and can never be torn down.
+ */
+
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+/**
+ * Loads a module by its path relative to this file's own directory.
+ *
+ * The plugin ships beside dist/backend, so in a built server the compiled
+ * .js for the moved Proxmox files (routes.js, ...) sits right next to this
+ * .mjs, and core modules resolve via ../../../backend/backend/... from
+ * there (dist/plugins/proxmox/backend -> dist/backend/backend). Under
+ * vitest/dev nothing imports this plugin directly (the loader loads
+ * in-process plugins with a plain dynamic import, no tsx loader involved),
+ * so the only layout that needs to resolve here is the built one.
+ */
+async function loadRelative(relativePath) {
+  const here = path.dirname(fileURLToPath(import.meta.url));
+  const target = path.join(here, `${relativePath}.js`);
+  return import(new URL(`file://${target.replace(/\\/g, "/")}`).href);
+}
+
+let routesModule = null;
+
+export async function activate(ctx) {
+  routesModule = await loadRelative("routes");
+  routesModule.startProxmoxService();
+  ctx.log.info("Proxmox router registered at /proxmox");
+}
+
+export async function deactivate() {
+  if (routesModule) {
+    routesModule.stopProxmoxService();
+    routesModule = null;
+  }
+}