route desktop guacd calls to the connected remote server (#1122)

resolveConnectionOrigin() pins RDP/VNC/Telnet to "remote" because the embedded
desktop backend does not bundle guacd, and the Guacamole websocket already
follows that. The status check and both token calls did not: they use the shared
authApi, which in Electron is hard-coded to the embedded backend.

So the desktop app asked the backend without guacd whether guacd was available,
got "disconnected", and refused to connect — while the connected server it would
actually have used reports it as connected and serves the same host fine from the
web client.

Send those three calls through a remote-origin instance in Electron, alongside
the existing file-manager, tunnel and stats ones.

Closes Termix-SSH/Support#1043

src/ui/main-axios.ts

@@ -763,6 +763,7 @@ function createRemoteOriginApiInstance(path: string): AxiosInstance {
 let remoteFileManagerApi: AxiosInstance | null = null;
 let remoteTunnelApi: AxiosInstance | null = null;
 let remoteStatsApi: AxiosInstance | null = null;
+let remoteGuacamoleApi: AxiosInstance | null = null;
 
 export function getRemoteFileManagerApi(): AxiosInstance {
   if (!remoteFileManagerApi) {
@@ -785,6 +786,13 @@ export function getRemoteStatsApi(): AxiosInstance {
   return remoteStatsApi;
 }
 
+export function getRemoteGuacamoleApi(): AxiosInstance {
+  if (!remoteGuacamoleApi) {
+    remoteGuacamoleApi = createRemoteOriginApiInstance("");
+  }
+  return remoteGuacamoleApi;
+}
+
 // Maps a live SSH session (keyed by sessionId, which today is the host's
 // numeric id as a string -- see ensureSSHSessionForHost) to the resolved
 // origin it was connected through, so every subsequent file-manager call