feat: 新增 MySQL 数据库驱动支持，支持跨设备数据同步

backend/internal/config/config_test.go

@@ -19,6 +19,12 @@ func TestDefaultConfig(t *testing.T) {
 	assert.Equal(t, 30*time.Second, cfg.Server.ReadTimeout)
 	assert.Equal(t, 30*time.Second, cfg.Server.WriteTimeout)
 
+	assert.Equal(t, "sqlite", cfg.Database.Driver)
+	assert.Equal(t, "", cfg.Database.Host)
+	assert.Equal(t, 3306, cfg.Database.Port)
+	assert.Equal(t, "", cfg.Database.User)
+	assert.Equal(t, "", cfg.Database.Password)
+	assert.Equal(t, "nex", cfg.Database.DBName)
 	assert.Equal(t, 10, cfg.Database.MaxIdleConns)
 	assert.Equal(t, 100, cfg.Database.MaxOpenConns)
 	assert.Equal(t, 1*time.Hour, cfg.Database.ConnMaxLifetime)
@@ -86,11 +92,76 @@ func TestConfig_Validate(t *testing.T) {
 			wantErr: false,
 		},
 		{
-			name:    "数据库路径为空无效",
+			name:    "SQLite模式路径为空无效",
 			modify:  func(c *Config) { c.Database.Path = "" },
 			wantErr: true,
 			errMsg:  "配置验证失败",
 		},
+		{
+			name:    "driver值不合法",
+			modify:  func(c *Config) { c.Database.Driver = "postgres" },
+			wantErr: true,
+			errMsg:  "配置验证失败",
+		},
+		{
+			name: "MySQL配置有效",
+			modify: func(c *Config) {
+				c.Database.Driver = "mysql"
+				c.Database.Host = "localhost"
+				c.Database.Port = 3306
+				c.Database.User = "root"
+				c.Database.DBName = "nex"
+				c.Database.Path = ""
+			},
+			wantErr: false,
+		},
+		{
+			name: "MySQL模式host为空无效",
+			modify: func(c *Config) {
+				c.Database.Driver = "mysql"
+				c.Database.Host = ""
+				c.Database.User = "root"
+				c.Database.DBName = "nex"
+				c.Database.Path = ""
+			},
+			wantErr: true,
+			errMsg:  "配置验证失败",
+		},
+		{
+			name: "MySQL模式user为空无效",
+			modify: func(c *Config) {
+				c.Database.Driver = "mysql"
+				c.Database.Host = "localhost"
+				c.Database.User = ""
+				c.Database.DBName = "nex"
+				c.Database.Path = ""
+			},
+			wantErr: true,
+			errMsg:  "配置验证失败",
+		},
+		{
+			name: "MySQL模式dbname为空无效",
+			modify: func(c *Config) {
+				c.Database.Driver = "mysql"
+				c.Database.Host = "localhost"
+				c.Database.User = "root"
+				c.Database.DBName = ""
+				c.Database.Path = ""
+			},
+			wantErr: true,
+			errMsg:  "配置验证失败",
+		},
+		{
+			name: "MySQL模式忽略path字段",
+			modify: func(c *Config) {
+				c.Database.Driver = "mysql"
+				c.Database.Host = "localhost"
+				c.Database.User = "root"
+				c.Database.DBName = "nex"
+				c.Database.Path = ""
+			},
+			wantErr: false,
+		},
 	}
 
 	for _, tt := range tests {
@@ -140,7 +211,10 @@ func TestSaveAndLoadConfig(t *testing.T) {
 			WriteTimeout: 20 * time.Second,
 		},
 		Database: DatabaseConfig{
+			Driver:          "sqlite",
 			Path:            filepath.Join(dir, "test.db"),
+			Port:            3306,
+			DBName:          "nex",
 			MaxIdleConns:    5,
 			MaxOpenConns:    50,
 			ConnMaxLifetime: 30 * time.Minute,
@@ -210,6 +284,9 @@ func TestConfigPriority(t *testing.T) {
 		assert.Equal(t, 9826, cfg.Server.Port)
 		assert.Equal(t, 30*time.Second, cfg.Server.ReadTimeout)
 		assert.Equal(t, 30*time.Second, cfg.Server.WriteTimeout)
+		assert.Equal(t, "sqlite", cfg.Database.Driver)
+		assert.Equal(t, 3306, cfg.Database.Port)
+		assert.Equal(t, "nex", cfg.Database.DBName)
 		assert.Equal(t, 10, cfg.Database.MaxIdleConns)
 		assert.Equal(t, 100, cfg.Database.MaxOpenConns)
 		assert.Equal(t, 1*time.Hour, cfg.Database.ConnMaxLifetime)
@@ -222,11 +299,19 @@ func TestConfigPriority(t *testing.T) {
 }
 
 func TestPrintSummary(t *testing.T) {
-	// 测试配置摘要输出
-	t.Run("打印配置摘要", func(t *testing.T) {
+	t.Run("SQLite模式摘要", func(t *testing.T) {
 		cfg := DefaultConfig()
-		// PrintSummary 只是打印，不会返回错误
-		// 这里主要验证不会 panic
+		assert.NotPanics(t, func() {
+			cfg.PrintSummary()
+		})
+	})
+	t.Run("MySQL模式摘要", func(t *testing.T) {
+		cfg := DefaultConfig()
+		cfg.Database.Driver = "mysql"
+		cfg.Database.Host = "db.example.com"
+		cfg.Database.Port = 3306
+		cfg.Database.User = "nex"
+		cfg.Database.DBName = "nex"
 		assert.NotPanics(t, func() {
 			cfg.PrintSummary()
 		})