refactor(channelserver): eliminate *sqlx.Rows/*sql.Rows from repository interfaces

Move scan loops from handlers into repository methods so that interfaces
return typed slices instead of leaking database cursors. This fixes
resource leaks (7 of 12 call sites never closed rows) and makes all
12 methods mockable for unit tests.

Affected repos: CafeRepo, ShopRepo, EventRepo, RengokuRepo, DivaRepo,
ScenarioRepo, MiscRepo, MercenaryRepo. New structs: DivaEvent,
MercenaryLoan, GuildHuntCatUsage. EventRepo.GetEventQuests left as-is
(requires broader Server refactor).

server/channelserver/repo_misc.go

@@ -1,7 +1,7 @@
 package channelserver
 
 import (
-	"database/sql"
+	"fmt"
 
 	"github.com/jmoiron/sqlx"
 )
@@ -17,8 +17,21 @@ func NewMiscRepository(db *sqlx.DB) *MiscRepository {
 }
 
 // GetTrendWeapons returns the top 3 weapon IDs for a given weapon type, ordered by count descending.
-func (r *MiscRepository) GetTrendWeapons(weaponType uint8) (*sql.Rows, error) {
-	return r.db.Query("SELECT weapon_id FROM trend_weapons WHERE weapon_type=$1 ORDER BY count DESC LIMIT 3", weaponType)
+func (r *MiscRepository) GetTrendWeapons(weaponType uint8) ([]uint16, error) {
+	rows, err := r.db.Query("SELECT weapon_id FROM trend_weapons WHERE weapon_type=$1 ORDER BY count DESC LIMIT 3", weaponType)
+	if err != nil {
+		return nil, fmt.Errorf("query trend_weapons: %w", err)
+	}
+	defer rows.Close()
+	var result []uint16
+	for rows.Next() {
+		var id uint16
+		if err := rows.Scan(&id); err != nil {
+			return nil, fmt.Errorf("scan trend_weapons: %w", err)
+		}
+		result = append(result, id)
+	}
+	return result, rows.Err()
 }
 
 // UpsertTrendWeapon increments the count for a weapon, inserting it if it doesn't exist.