Replace GORM with bbolt for database operations

Migrated from GORM to bbolt for lightweight key-value storage, better aligning with project requirements. Updated repository methods to utilize bbolt's native APIs and removed dependencies associated with GORM.

migration/migration.go

@@ -1,15 +1,12 @@
 package migration
 
 import (
-	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/setting"
-	"gorm.io/gorm"
+	"go.etcd.io/bbolt"
 )
 
-func Run(db *gorm.DB) error {
-	err := db.AutoMigrate(&setting.Setting{})
-	if err != nil {
+func Run(db *bbolt.DB) error {
+	return db.Update(func(tx *bbolt.Tx) error {
+		_, err := tx.CreateBucketIfNotExists([]byte("settings"))
 		return err
-	}
-
-	return nil
+	})
 }