feat: wire remote-desktop plugin into core and rename i18n keys

Repoints core consumers (dispatcher, collab, session-sharing, tab
utils) at the plugin, adds isTabTypeAvailable gating for rdp/vnc/
telnet, widens hostCapability to accept an array, and renames the
guacamole i18n namespace to remoteDesktop.

src/backend/database/database.ts

@@ -15,7 +15,7 @@ import workspaceRoutes from "./routes/workspaces.js";
 import c2sTunnelPresetRoutes from "./routes/c2s-tunnel-presets.js";
 import terminalRoutes from "./routes/terminal.js";
 import sessionLogRoutes from "./routes/session-log-routes.js";
-import guacamoleRoutes from "../hosts/guacamole/routes.js";
+import guacamoleDispatch from "./routes/guacamole-dispatch.js";
 import sessionSharingRoutes from "../hosts/session-sharing/routes.js";
 import collabRoutes from "../hosts/collab/routes.js";
 import networkTopologyRoutes from "./routes/network-topology.js";
@@ -1758,7 +1758,7 @@ app.use("/workspaces", workspaceRoutes);
 app.use("/c2s-tunnel-presets", c2sTunnelPresetRoutes);
 app.use("/terminal", terminalRoutes);
 app.use("/session_logs", sessionLogRoutes);
-app.use("/guacamole", guacamoleRoutes);
+app.use("/guacamole", guacamoleDispatch);
 app.use("/session-sharing", sessionSharingRoutes);
 app.use("/collab", collabRoutes);
 app.use("/network-topology", networkTopologyRoutes);

src/backend/database/routes/user-settings-routes.ts

@@ -1,7 +1,12 @@
 import type { AuthenticatedRequest } from "../../../types/index.js";
 import { getErrorMessage } from "../../utils/error-message.js";
 import type { RequestHandler, Router } from "express";
-import { restartGuacServer } from "../../hosts/guacamole/guacamole-server.js";
+// Remote Desktop is a first-party plugin (plugins/remote-desktop); this goes
+// through the same in-core bridge its router is mounted behind, rather than
+// importing the plugin's TypeScript directly, since plugins/ is compiled
+// separately from src/backend/ and core cannot statically import across that
+// boundary. See guacamole-dispatch.ts and that plugin's README.
+import { restartGuacamoleService as restartGuacServer } from "./guacamole-dispatch.js";
 import {
   authLogger,
   getGlobalLogLevel,