Textgen: Add permissions check for TabbyAPI keys

There's no formal permissions checking in ST's UI, so add a temporary
check in the server endpoint before requesting a download.

Signed-off-by: kingbri <bdashore3@proton.me>

public/scripts/textgen-models.js

@@ -526,7 +526,10 @@ async function downloadTabbyModel() {
             body: JSON.stringify(params),
         });
 
-        if (!response.ok) {
+        if (response.status === 403) {
+            toastr.error("The provided key has invalid permissions. Please use an admin key for downloading.");
+            return;
+        } else if (!response.ok) {
             throw new Error(response.statusText);
         }