fix: Prevent using disabled proxy from crawling defaults

[SuaYoo]

Resolves #3278

Changes

• Fixes edge case where a proxy that is no longer enabled from an org is used.
• Fixes incorrect value passed for default proxy ID.

Manual testing

1. Log in as superadmin
2. Enable us-proxy-2 on an org
3. Go to org settings
4. Set us-proxy-2 as default from org settings
5. Go to superadmin dashboard
6. Remove us-proxy-2 from org from superadmin dashboard
7. Go to org dashboard
8. Go to New Browser Profile > Start Browser. Verify that us-proxy-2 is not selected

Follow-ups

This change doesn't actually remove the disabled proxy from crawling defaults, just checks if the proxy ID specified as a crawling default exists in the org proxy server list. We may want to update the backend to remove the proxy from crawling defaults when it's disabled by a superadmin (cc @tw4l.)

[tw4l]

@SuaYoo @emma-sg Hope you don't mind, since it was a quick addition I added a backend commit so we can just wrap this up here and not require a follow-up :) I've tested locally to ensure it works when both individual and shared proxies are removed from an org.

[SuaYoo]

@SuaYoo @emma-sg Hope you don't mind, since it was a quick addition I added a backend commit so we can just wrap this up here and not require a follow-up :) I've tested locally to ensure it works when both individual and shared proxies are removed from an org.

Manually tested on dev, looks good!