Fix errcheck violations across 11 repo files by wrapping deferred
rows.Close() and tx.Rollback() calls to discard the error return.
Fix unchecked Scan/Exec calls in guild store tests. Fix staticcheck
SA9003 empty branch in test helpers.
Add 6 mock-based unit tests for GetCharacterSaveData covering nil
savedata, sql.ErrNoRows, DB errors, compressed round-trip,
new-character skip, and config mode/pointer propagation.
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.
