[Bug]: /quick ai error messages are not role-aware and lack actionable guidance

Description

When /quick ai is used without a configured API key or URL, the error messages shown in the AI modal are not helpful:

• Admins see "Please contact your administrator" even though they ARE the admin
• Personal mode users see "Please check your configuration" with no direction on where to fix it
• All error messages are the same regardless of the user's role
• Running /quick ai in an empty room silently does nothing
• App settings mark all fields as required even though only the selected provider's fields need to be filled

Expected behavior

• Admins should see "Please add the required API key or URL in the app settings"
• Regular workspace users should see "The required API key or URL is missing. Please contact your administrator"
• Personal mode users should see "Please set up your API key or URL using /quick config"
• Running /quick ai in an empty room should show a notification
• App settings should not show required markers on optional fields

Steps to reproduce

1. Install the Quick Replies app
2. Do not configure any AI API key
3. Run /quick ai, type a prompt, click Generate
4. Observe: admin sees "contact your administrator" error
5. Also try in an empty channel — nothing happens

Version

Version 8.1.1

What browsers are you seeing the problem on?

Chrome

Start by reproducing /quick ai with no API key or URL, including in an empty room, then inspect the AI modal, app settings, and /quick config entry points. Done means role-specific actionable errors, a notification for empty rooms, and required markers only for fields used by the selected provider.