feat(forum): add support for comment_role_id field

[wescopeland]

https://discord.com/channels/310192285306454017/1499468217654051137/1503387011774550116

sail artisan migrate

This PR adds a nullable comment_role_id field to forum_topics. When it's set:

• Normal (non-staff) users may no longer comment on the forum topic - it's effectively locked for them.
• Users with the role may reply as themselves.
• Users with the role may reply as any team account they have access to that also has the role.
• Moderators bypass the role gate and can still always reply.

At the moment, this can only be set on a topic by manually doing it in the database. It may be desirable in the future to make this editable in the front-end moderation controls. This is a QoL concern that I think that would more than double the size of this PR, so I decided to punt it for now.

As a QA member when the topic has comment_role_id=25

As a regular user when the topic has comment_role_id=25