feat: move remote desktop (RDP/VNC/Telnet) into a first-party plugin

Relocates guacamole backend/frontend source and tests into
plugins/remote-desktop, following the ssh-terminal/docker pattern.

src/backend/database/routes/guacamole-dispatch.ts

@@ -0,0 +1,113 @@
+// Mounted at /guacamole. Remote Desktop ships as a first-party in-process
+// plugin (plugins/remote-desktop) rather than a route file imported directly
+// here, so this module keeps /guacamole/* working at its original path
+// without handing the plugin a reference to the shared app instance.
+//
+// It also brokers the small surface collab, session-sharing and the admin
+// settings route need from the plugin (join tokens, live-session lookups, a
+// server restart hook). Those core modules cannot import the plugin's
+// TypeScript directly -- plugins/ is compiled by tsconfig.plugins.json as a
+// one-directional read of src/backend/ (see copy-bundled-plugins.cjs), and a
+// core file under tsconfig.node.json's rootDir cannot statically import
+// something outside it. So the plugin registers this bridge once on
+// activate, and clears it on deactivate; a disabled/uninstalled plugin falls
+// back to the safe defaults below (404 for the router, null for session
+// lookups, a no-op restart).
+//
+// This is an accepted, temporary coupling -- see the plugin's own README.
+// collab and session-sharing are expected to become plugins of their own
+// later, at which point this becomes a real inter-plugin service reference
+// instead of a bridge object living in core.
+//
+// The router forwards with no auth of its own: it delegates to exactly one
+// first-party router, and every route in that router already applies its
+// own auth middleware.
+
+import type { Request, Response, NextFunction, Router } from "express";
+import { databaseLogger } from "../../utils/logger.js";
+
+export interface GuacamoleSessionInfo {
+  guacamoleConnectionId: string;
+  hostId: number;
+  ownerUserId: string;
+  protocol: string;
+  openedAt: number;
+}
+
+export interface GuacamoleBridge {
+  router: Router;
+  restart: () => Promise<void>;
+  createJoinToken: (guacamoleConnectionId: string, readOnly: boolean) => string;
+  getSessionInfo: (
+    guacamoleConnectionId: string,
+  ) => GuacamoleSessionInfo | null;
+}
+
+let bridge: GuacamoleBridge | null = null;
+
+export function registerGuacamoleBridge(next: GuacamoleBridge): void {
+  bridge = next;
+  databaseLogger.info("Registered Remote Desktop plugin bridge", {
+    operation: "guacamole_dispatch_register",
+  });
+}
+
+export function unregisterGuacamoleBridge(): void {
+  if (!bridge) return;
+  bridge = null;
+  databaseLogger.info("Unregistered Remote Desktop plugin bridge", {
+    operation: "guacamole_dispatch_register",
+  });
+}
+
+/**
+ * Restarts the plugin's guacd WebSocket server, e.g. after an admin edits
+ * the guacd URL setting (see user-settings-routes.ts). A no-op while the
+ * plugin is disabled/uninstalled -- restarting a server that does not exist
+ * would otherwise silently resurrect it outside the plugin lifecycle.
+ */
+export async function restartGuacamoleService(): Promise<void> {
+  if (!bridge) return;
+  await bridge.restart();
+}
+
+/**
+ * Mints a read-only/writable join token for an existing live Guacamole
+ * session, for collab/session-sharing to hand to an invited viewer. Throws
+ * when the plugin is disabled/uninstalled -- unlike the read-only lookups
+ * below, a caller asking to mint a join token needs to know it failed rather
+ * than silently getting an unusable value.
+ */
+export function createGuacamoleJoinToken(
+  guacamoleConnectionId: string,
+  readOnly: boolean,
+): string {
+  if (!bridge) {
+    throw new Error("Remote Desktop plugin is not available");
+  }
+  return bridge.createJoinToken(guacamoleConnectionId, readOnly);
+}
+
+/**
+ * Looks up a live Guacamole session by guacd's own connection id. Returns
+ * null both when no such session exists and when the plugin is
+ * disabled/uninstalled -- to a caller checking "is this session live", the
+ * two cases mean the same thing.
+ */
+export function getGuacamoleSessionInfo(
+  guacamoleConnectionId: string,
+): GuacamoleSessionInfo | null {
+  return bridge?.getSessionInfo(guacamoleConnectionId) ?? null;
+}
+
+export default function guacamoleDispatch(
+  req: Request,
+  res: Response,
+  next: NextFunction,
+): void {
+  if (!bridge) {
+    res.status(404).json({ error: "Remote Desktop is not available" });
+    return;
+  }
+  bridge.router(req, res, next);
+}