refactor(channelserver): extract Goocoo, Diva, Misc, Scenario, and Mercenary repositories

Move remaining raw s.server.db.* queries from handler files into
dedicated repository structs, completing the repository extraction
effort. Also adds SaveCharacterData and SaveHouseData to
CharacterRepository.

Fixes guild_hunts query to select both cats_used and start columns
to match the existing two-column Scan call. Adds slot index
validation in GoocooRepository to prevent SQL injection via
fmt.Sprintf.

server/channelserver/repo_mercenary.go

@@ -0,0 +1,50 @@
+package channelserver
+
+import (
+	"database/sql"
+
+	"github.com/jmoiron/sqlx"
+)
+
+// MercenaryRepository centralizes database access for mercenary/rasta/airou sequences and queries.
+type MercenaryRepository struct {
+	db *sqlx.DB
+}
+
+// NewMercenaryRepository creates a new MercenaryRepository.
+func NewMercenaryRepository(db *sqlx.DB) *MercenaryRepository {
+	return &MercenaryRepository{db: db}
+}
+
+// NextRastaID returns the next value from the rasta_id_seq sequence.
+func (r *MercenaryRepository) NextRastaID() (uint32, error) {
+	var id uint32
+	err := r.db.QueryRow("SELECT nextval('rasta_id_seq')").Scan(&id)
+	return id, err
+}
+
+// NextAirouID returns the next value from the airou_id_seq sequence.
+func (r *MercenaryRepository) NextAirouID() (uint32, error) {
+	var id uint32
+	err := r.db.QueryRow("SELECT nextval('airou_id_seq')").Scan(&id)
+	return id, err
+}
+
+// GetMercenaryLoans returns characters that have a pact with the given character's rasta_id.
+func (r *MercenaryRepository) GetMercenaryLoans(charID uint32) (*sql.Rows, error) {
+	return r.db.Query("SELECT name, id, pact_id FROM characters WHERE pact_id=(SELECT rasta_id FROM characters WHERE id=$1)", charID)
+}
+
+// GetGuildHuntCatsUsed returns cats_used and start from guild_hunts for a given character.
+func (r *MercenaryRepository) GetGuildHuntCatsUsed(charID uint32) (*sql.Rows, error) {
+	return r.db.Query(`SELECT cats_used, start FROM guild_hunts gh
+		INNER JOIN characters c ON gh.host_id = c.id WHERE c.id=$1`, charID)
+}
+
+// GetGuildAirou returns otomoairou data for all characters in a guild.
+func (r *MercenaryRepository) GetGuildAirou(guildID uint32) (*sql.Rows, error) {
+	return r.db.Query(`SELECT c.otomoairou FROM characters c
+	INNER JOIN guild_characters gc ON gc.character_id = c.id
+	WHERE gc.guild_id = $1 AND c.otomoairou IS NOT NULL
+	ORDER BY c.id LIMIT 60`, guildID)
+}