Return []EventQuest instead of a raw database cursor, removing the last
*sql.Rows leak from the repository layer. The handler now iterates a
slice, and makeEventQuest reads fields from the struct directly instead
of scanning rows twice. This makes the method fully mockable and
eliminates the risk of unclosed cursors.
Cover the three repository methods added in the previous commit:
- CharacterRepo.LoadSaveData: normal, new-character, and not-found cases
- EventRepo.GetEventQuests: empty, multi-row, ordering, tx commit/rollback
- UserRepo.BanUser: permanent, temporary, and both upsert directions
