Add troubleshooting steps for Kaspersky Antivirus sign-in issue (#908)

The new content provides guidance for users experiencing a stuck sign-in dialog due to Kaspersky Antivirus interference. It includes the problem description, solution steps, and a warning to re-enable protection after signing in.

Author: jdorfman

docs/cody/faq.mdx

@@ -137,6 +137,22 @@ cody chat --model '$name_of_the_model' -m 'Hi Cody!'
 
 For example, to use Claude 3.5 Sonnet, you'd pass the following command in your terminal, `cody chat --model 'claude-3.5-sonnet' -m 'Hi Cody!'
 
+### Sign-in dialog gets stuck with Kaspersky Antivirus
+
+**Problem:** When attempting to sign in, users may encounter a perpetual `"Signing in to Sourcegraph..."` dialog that never completes. This issue persists across different VS Code extension versions (e.g. 1.40-1.48) and browsers (Chrome, Edge, Firefox). In the browser console at `accounts.sourcegraph.com/sign-in`, you might see an error: `"Uncaught ApolloError: value.toString is not a function"`.
+
+**Solution:** This issue is typically caused by Kaspersky Antivirus interfering with the authentication process. To resolve:
+
+- Locate the Kaspersky icon in your system tray
+- Right-click on the Kaspersky icon
+- Select "Stop Protection"
+- Right-click the icon again
+- Select "Exit"
+
+<Callout type="warning">
+Once you are signed in make sure to re-enable protection.
+</Callout>
+
 ## OpenAI o1
 
 ### What are OpenAI o1 best practices?