refactor(channelserver): move remaining s.server.db calls into repositories

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

server/channelserver/repo_user.go

@@ -2,6 +2,7 @@ package channelserver
 
 import (
 	"database/sql"
+	"time"
 
 	"github.com/jmoiron/sqlx"
 )
@@ -218,3 +219,16 @@ func (r *UserRepository) GetByIDAndUsername(charID uint32) (userID uint32, usern
 	).Scan(&userID, &username)
 	return
 }
+
+// BanUser inserts or updates a ban for the given user.
+// A nil expires means a permanent ban; non-nil sets a temporary ban with expiry.
+func (r *UserRepository) BanUser(userID uint32, expires *time.Time) error {
+	if expires == nil {
+		_, err := r.db.Exec(`INSERT INTO bans VALUES ($1)
+			ON CONFLICT (user_id) DO UPDATE SET expires=NULL`, userID)
+		return err
+	}
+	_, err := r.db.Exec(`INSERT INTO bans VALUES ($1, $2)
+		ON CONFLICT (user_id) DO UPDATE SET expires=$2`, userID, *expires)
+	return err
+}