Eliminate the last three direct DB accesses from handler code:
- CharacterRepo.LoadSaveData: replaces db.Query in GetCharacterSaveData,
using QueryRow instead of Query+Next for cleaner single-row access
- EventRepo.GetEventQuests, UpdateEventQuestStartTime, BeginTx: moves
event quest enumeration and rotation queries behind the repo layer
- UserRepo.BanUser: consolidates permanent/temporary ban upserts into a
single method with nil/*time.Time semantics
Leverage the new repository interfaces to test handler logic without
a database. Adds shared mock implementations (achievement, mail,
character, goocoo, guild) and 32 new handler tests covering
achievement, mail, cafe/boost, and goocoo handlers.
