Fix email attachment collisions causing email send failure

[yungcomputerchair]

Unclaimed email attachments are currently not deleted if the email is deleted.
This is because email attachments are not formally related to emails in the DB with the current schema, so there's no way to ON DELETE CASCADE them.
Since email message indices are reused, the orphaned attachments can overlap with attachments in new emails, preventing them from being sent due to the UNIQUE constraint in the attachment table failing.

We don't want to change the schema, but we can fix this entirely in code, which is what this PR does.
For prevention: delete all email attachments when an email is deleted
For remediation: when the DB error is hit, attempt to delete the attachments from the deleted email, then try sending again

There was also a bad semicolon in one of the SQL queries which I think can cause some issues with attachment claiming; that has been fixed too.

[FinnHornhoover]

On master:

[Email] (GM) Kuki Jamlocke [2] (to (GM) Bodhi Cutecannon [1]): <No subject.>

[WARN] Database: Failed to send email: UNIQUE constraint failed: EmailItems.PlayerID, EmailItems.MsgIndex, EmailItems.Slot

On mailfix:
I'm able to send a second mail with attachments even if the other player deleted the first mail with attachment. Tried twice.

Getting into a broken state in master and then recompiling in mailfix, then trying to send another mail with attachment works without issues.

[FinnHornhoover]

Looks good to go 👍