Better Remote Connections for Desktop

**What problem would this solve?**
* The remote backend feature of the desktop app has several issues
* It does not follow redirects
* It cannot supply a client cert for hosts that require mTLS
* It does not have a way for the user to test the connection before enabling it
* It requires a new window, but when the connection doesn't work for any reason the window just never opens, it times out and you get a system dialog saying to disable it and re-open. There is no way to figure out what the error with the connection is

**What would a good outcome look like?**
* A version that connects in the same window
* A "test connection" button that shows what's working and any errors encountered

**Possible approaches**
* Route the ACP connection through the `main.ts` node process side for more control over the connection (certs, redirect following, etc) and relay that info to the renderer side

**Additional context**
N/A

- [x] I have verified this does not duplicate an existing feature request

Do not begin implementation until the issue reaches **Ready** on the [Goose Issues board](https://github.com/orgs/aaif-goose/projects/1).

Das Issue erwähnt, die ACP-Verbindung über den node-Prozess in der Datei main.ts zu routen. Untersuche zunächst den Remote-Backend-Code der Desktop-App, wahrscheinlich in der Datei main.ts und den zugehörigen IPC-Modulen (Interprozesskommunikation). Suche nach bestehender Verbindungsbehandlung und Fehlerberichterstattung. Eine Schaltfläche „Verbindung testen“ würde UI-Änderungen im Renderer und neue IPC-Nachrichten an den Hauptprozess erfordern. „Erledigt“ bedeutet, dass die Verbindung Weiterleitungen folgen, mTLS-Clientzertifikate unterstützen und Diagnosefehler im selben Fenster anzeigen kann.

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