refactor(channelserver): extract CharacterRepository for characters table access

Centralizes all characters table SQL behind a CharacterRepository struct
in repo_character.go. The 4 existing helpers (loadCharacterData,
saveCharacterData, readCharacterInt, adjustCharacterInt) now delegate to
the repository, keeping identical signatures so all ~70 callsites remain
unchanged. Direct queries in handlers_session.go, sys_channel_server.go
(DisconnectUser), and handlers_mail.go are also migrated.

Pure refactor with zero behavior change — first step toward eliminating
the ~130 scattered character queries identified in anti-patterns #9.

server/channelserver/repo_character.go

@@ -0,0 +1,76 @@
+package channelserver
+
+import "github.com/jmoiron/sqlx"
+
+// CharacterRepository centralizes all database access for the characters table.
+type CharacterRepository struct {
+	db *sqlx.DB
+}
+
+// NewCharacterRepository creates a new CharacterRepository.
+func NewCharacterRepository(db *sqlx.DB) *CharacterRepository {
+	return &CharacterRepository{db: db}
+}
+
+// LoadColumn reads a single []byte column by character ID.
+func (r *CharacterRepository) LoadColumn(charID uint32, column string) ([]byte, error) {
+	var data []byte
+	err := r.db.QueryRow("SELECT "+column+" FROM characters WHERE id = $1", charID).Scan(&data)
+	return data, err
+}
+
+// SaveColumn writes a single []byte column by character ID.
+func (r *CharacterRepository) SaveColumn(charID uint32, column string, data []byte) error {
+	_, err := r.db.Exec("UPDATE characters SET "+column+"=$1 WHERE id=$2", data, charID)
+	return err
+}
+
+// ReadInt reads a single integer column (0 for NULL) by character ID.
+func (r *CharacterRepository) ReadInt(charID uint32, column string) (int, error) {
+	var value int
+	err := r.db.QueryRow("SELECT COALESCE("+column+", 0) FROM characters WHERE id=$1", charID).Scan(&value)
+	return value, err
+}
+
+// AdjustInt atomically adds delta to an integer column and returns the new value.
+func (r *CharacterRepository) AdjustInt(charID uint32, column string, delta int) (int, error) {
+	var value int
+	err := r.db.QueryRow(
+		"UPDATE characters SET "+column+"=COALESCE("+column+", 0)+$1 WHERE id=$2 RETURNING "+column,
+		delta, charID,
+	).Scan(&value)
+	return value, err
+}
+
+// GetName returns the character name by ID.
+func (r *CharacterRepository) GetName(charID uint32) (string, error) {
+	var name string
+	err := r.db.QueryRow("SELECT name FROM characters WHERE id=$1", charID).Scan(&name)
+	return name, err
+}
+
+// GetUserID returns the owning user_id for a character.
+func (r *CharacterRepository) GetUserID(charID uint32) (uint32, error) {
+	var userID uint32
+	err := r.db.QueryRow("SELECT user_id FROM characters WHERE id=$1", charID).Scan(&userID)
+	return userID, err
+}
+
+// UpdateLastLogin sets the last_login timestamp.
+func (r *CharacterRepository) UpdateLastLogin(charID uint32, timestamp int64) error {
+	_, err := r.db.Exec("UPDATE characters SET last_login=$1 WHERE id=$2", timestamp, charID)
+	return err
+}
+
+// UpdateTimePlayed sets the time_played value.
+func (r *CharacterRepository) UpdateTimePlayed(charID uint32, timePlayed int) error {
+	_, err := r.db.Exec("UPDATE characters SET time_played=$1 WHERE id=$2", timePlayed, charID)
+	return err
+}
+
+// GetCharIDsByUserID returns all character IDs belonging to a user.
+func (r *CharacterRepository) GetCharIDsByUserID(userID uint32) ([]uint32, error) {
+	var ids []uint32
+	err := r.db.Select(&ids, "SELECT id FROM characters WHERE user_id=$1", userID)
+	return ids, err
+}