fix: 发布产物自包含数据库迁移资源，修复 macOS DMG 安装后无法启动

使用 go:embed 嵌入迁移 SQL 到二进制，移除 runtime.Caller 源码路径依赖，
server 和 desktop 发布产物均可在无源码目录环境下完成数据库初始化和迁移。

backend/internal/database/database.go

@@ -1,10 +1,10 @@
 package database
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"path/filepath"
-	"runtime"
 
 	"github.com/pressly/goose/v3"
 	"go.uber.org/zap"
@@ -13,6 +13,7 @@ import (
 	"gorm.io/gorm"
 
 	"nex/backend/internal/config"
+	"nex/backend/migrations"
 	pkglogger "nex/backend/pkg/logger"
 )
 
@@ -77,29 +78,24 @@ func runMigrations(db *gorm.DB, driver string, zapLogger *zap.Logger) error {
 		return err
 	}
 
-	gooseDialect := "sqlite3"
-	migrationsSubDir := "sqlite"
-	if driver == "mysql" {
-		gooseDialect = "mysql"
-		migrationsSubDir = "mysql"
-	}
-
-	migrationsDir := getMigrationsDir(driver)
-	if _, err := os.Stat(migrationsDir); os.IsNotExist(err) {
-		return fmt.Errorf("迁移目录不存在: %s", migrationsDir)
+	dialect, fsys, err := migrations.ForDriver(driver)
+	if err != nil {
+		return err
 	}
 
 	if zapLogger != nil {
 		zapLogger.Info("执行数据库迁移",
-			zap.String("dialect", gooseDialect),
-			zap.String("dir", migrationsSubDir))
+			zap.String("dialect", string(dialect)),
+			zap.String("driver", driver))
 	}
 
-	if err := goose.SetDialect(gooseDialect); err != nil {
-		return err
+	provider, err := goose.NewProvider(dialect, sqlDB, fsys)
+	if err != nil {
+		return fmt.Errorf("创建迁移提供者失败: %w", err)
 	}
-	if err := goose.Up(sqlDB, migrationsDir); err != nil {
-		return err
+
+	if _, err := provider.Up(context.Background()); err != nil {
+		return fmt.Errorf("执行迁移失败: %w", err)
 	}
 
 	return nil
@@ -130,21 +126,6 @@ func configurePool(db *gorm.DB, cfg *config.DatabaseConfig, zapLogger *zap.Logge
 	}
 }
 
-func getMigrationsDir(driver string) string {
-	_, filename, _, ok := runtime.Caller(0)
-	if ok {
-		subDir := "sqlite"
-		if driver == "mysql" {
-			subDir = "mysql"
-		}
-		dir := filepath.Join(filepath.Dir(filename), "..", "..", "migrations", subDir)
-		if abs, err := filepath.Abs(dir); err == nil {
-			return abs
-		}
-	}
-	return "./migrations"
-}
-
 func BuildDSN(cfg *config.DatabaseConfig) string {
 	return fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?charset=utf8mb4&parseTime=true&loc=Local",
 		cfg.User, cfg.Password, cfg.Host, cfg.Port, cfg.DBName)

backend/internal/database/database_test.go

@@ -1,10 +1,13 @@
 package database
 
 import (
+	"io/fs"
+	"os"
 	"path/filepath"
 	"testing"
 
 	"nex/backend/internal/config"
+	"nex/backend/migrations"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -76,3 +79,87 @@ func TestBuildDSN_EmptyPassword(t *testing.T) {
 	dsn := BuildDSN(cfg)
 	assert.Equal(t, "root:@tcp(localhost:3306)/nex?charset=utf8mb4&parseTime=true&loc=Local", dsn)
 }
+
+func TestInit_SQLite_AnyCWD(t *testing.T) {
+	dir := t.TempDir()
+
+	origDir, err := os.Getwd()
+	if err == nil {
+		defer func() {
+			if chdirErr := os.Chdir(origDir); chdirErr != nil {
+				t.Logf("无法恢复工作目录: %v", chdirErr)
+			}
+		}()
+	}
+	if chdirErr := os.Chdir(dir); chdirErr != nil {
+		t.Skipf("无法切换到临时目录: %v", chdirErr)
+	}
+
+	cfg := &config.DatabaseConfig{
+		Driver:          "sqlite",
+		Path:            filepath.Join(dir, "test.db"),
+		MaxIdleConns:    5,
+		MaxOpenConns:    10,
+		ConnMaxLifetime: 0,
+	}
+
+	zapLogger := zap.NewNop()
+	db, err := Init(cfg, zapLogger)
+	require.NoError(t, err)
+	require.NotNil(t, db)
+	defer Close(db)
+
+	sqlDB, err := db.DB()
+	require.NoError(t, err)
+	require.NotNil(t, sqlDB)
+}
+
+func TestForDriverDialect_SQLite(t *testing.T) {
+	require.NoError(t, testMigrateWithDriver(t, "sqlite"))
+}
+
+func TestForDriverDialect_MySQL(t *testing.T) {
+	dialect, fsys, err := migrations.ForDriver("mysql")
+	require.NoError(t, err)
+	assert.Equal(t, "mysql", string(dialect))
+	entries, fsErr := fs.ReadDir(fsys, ".")
+	require.NoError(t, fsErr)
+	assert.NotEmpty(t, entries, "MySQL 迁移资源应至少包含一个文件")
+}
+
+func TestForDriverDialect_Invalid(t *testing.T) {
+	dir := t.TempDir()
+	cfg := &config.DatabaseConfig{
+		Driver:          "postgres",
+		Path:            filepath.Join(dir, "test.db"),
+		MaxIdleConns:    5,
+		MaxOpenConns:    10,
+		ConnMaxLifetime: 0,
+	}
+
+	zapLogger := zap.NewNop()
+	_, err := Init(cfg, zapLogger)
+	assert.Error(t, err, "非法 driver 应返回错误")
+	assert.Contains(t, err.Error(), "不支持的数据库驱动")
+}
+
+func testMigrateWithDriver(t *testing.T, driver string) error {
+	t.Helper()
+
+	dir := t.TempDir()
+	cfg := &config.DatabaseConfig{
+		Driver:          driver,
+		Path:            filepath.Join(dir, "test.db"),
+		MaxIdleConns:    5,
+		MaxOpenConns:    10,
+		ConnMaxLifetime: 0,
+	}
+
+	zapLogger := zap.NewNop()
+	db, err := Init(cfg, zapLogger)
+	if err != nil {
+		return err
+	}
+	Close(db)
+	return nil
+}

backend/internal/database/embedded_migration_test.go

@@ -0,0 +1,71 @@
+package database
+
+import (
+	"io/fs"
+	"testing"
+
+	"nex/backend/migrations"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEmbeddedMigrations_SQLiteResourcesPresent(t *testing.T) {
+	entries, err := fs.ReadDir(migrations.FS, "sqlite")
+	require.NoError(t, err)
+
+	var sqlFiles []string
+	for _, entry := range entries {
+		if !entry.IsDir() {
+			sqlFiles = append(sqlFiles, entry.Name())
+		}
+	}
+	assert.NotEmpty(t, sqlFiles, "SQLite 迁移资源应至少包含一个 .sql 文件")
+}
+
+func TestEmbeddedMigrations_MySQLResourcesPresent(t *testing.T) {
+	entries, err := fs.ReadDir(migrations.FS, "mysql")
+	require.NoError(t, err)
+
+	var sqlFiles []string
+	for _, entry := range entries {
+		if !entry.IsDir() {
+			sqlFiles = append(sqlFiles, entry.Name())
+		}
+	}
+	assert.NotEmpty(t, sqlFiles, "MySQL 迁移资源应至少包含一个 .sql 文件")
+}
+
+func TestEmbeddedMigrations_SQLiteSQLParsable(t *testing.T) {
+	subFS, err := fs.Sub(migrations.FS, "sqlite")
+	require.NoError(t, err)
+
+	entries, err := fs.ReadDir(subFS, ".")
+	require.NoError(t, err)
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		data, err := fs.ReadFile(subFS, entry.Name())
+		require.NoError(t, err, "无法读取迁移文件: %s", entry.Name())
+		assert.NotEmpty(t, data, "迁移文件内容不应为空: %s", entry.Name())
+	}
+}
+
+func TestEmbeddedMigrations_MySQLSQLParsable(t *testing.T) {
+	subFS, err := fs.Sub(migrations.FS, "mysql")
+	require.NoError(t, err)
+
+	entries, err := fs.ReadDir(subFS, ".")
+	require.NoError(t, err)
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		data, err := fs.ReadFile(subFS, entry.Name())
+		require.NoError(t, err, "无法读取迁移文件: %s", entry.Name())
+		assert.NotEmpty(t, data, "迁移文件内容不应为空: %s", entry.Name())
+	}
+}