Review - Inactive accounts due to last team member being removed

We need to review the Inactive accounts that went into this state due to the client removing the last team member on the account.

Things to consider:

- we should put in a blocker so no account can be deactivated if there is only 1 team member.
- Client cannot remove themselves if they are the only team member.
- A review of the INACTIVE accounts columns shows there is a large amount of account that do not have any team members.
See historical data for acct 105061. Client removed themselves then the account deactivated.

Ideas:
1. For PAD accounts, when deactivation is prevented, put a useful message
2. When removing last team member, put a warning that this will deactivate your account

No files or tests are named. Start by tracing the account deactivation and last-team-member removal flows described in the issue, using historical data for account 105061 as a reference. Define the blocking and warning behavior, including the PAD-account message, and add coverage for the affected flows.

Written by the indexing model from the issue text.