fix: 修复应用设置保存时未传字段被覆盖为空值/默认值的问题

backend/internal/router/admin/applications.go

@@ -367,31 +367,61 @@ func handleUpdateApplication(c *gin.Context) {
 
 	app.Name = req.Name
 	app.Description = req.Description
-	app.BillingType = req.BillingType
-	app.LoginPolicy = req.LoginPolicy
+	if req.BillingType != "" {
+		app.BillingType = req.BillingType
+	}
+	if req.LoginPolicy != "" {
+		app.LoginPolicy = req.LoginPolicy
+	}
 	app.AllowRegister = req.AllowRegister
 	app.EnableLoginVerify = req.EnableLoginVerify
 	app.EnableRegisterVerify = req.EnableRegisterVerify
-	app.VerifyMethod = req.VerifyMethod
+	if req.VerifyMethod != "" {
+		app.VerifyMethod = req.VerifyMethod
+	}
 	app.EmailConfigID = req.EmailConfigID
 	app.SmsConfigID = req.SmsConfigID
-	app.EncryptType = req.EncryptType
+	if req.EncryptType != "" {
+		app.EncryptType = req.EncryptType
+	}
 	if req.EncryptKey != "" {
 		app.EncryptKey = req.EncryptKey
 	}
-	app.BindType = req.BindType
-	app.MaxDevices = req.MaxDevices
-	app.ChangeLimit = req.ChangeLimit
-	app.ChangeInterval = req.ChangeInterval
-	app.ChangeExceedAction = req.ChangeExceedAction
-	app.ChangeDeductAmount = req.ChangeDeductAmount
-	app.MultiOpenMode = req.MultiOpenMode
-	app.MaxInstances = req.MaxInstances
+	if req.BindType != "" {
+		app.BindType = req.BindType
+	}
+	if req.MaxDevices > 0 {
+		app.MaxDevices = req.MaxDevices
+	}
+	if req.ChangeLimit > 0 {
+		app.ChangeLimit = req.ChangeLimit
+	}
+	if req.ChangeInterval > 0 {
+		app.ChangeInterval = req.ChangeInterval
+	}
+	if req.ChangeExceedAction != "" {
+		app.ChangeExceedAction = req.ChangeExceedAction
+	}
+	if req.ChangeDeductAmount > 0 {
+		app.ChangeDeductAmount = req.ChangeDeductAmount
+	}
+	if req.MultiOpenMode != "" {
+		app.MultiOpenMode = req.MultiOpenMode
+	}
+	if req.MaxInstances > 0 {
+		app.MaxInstances = req.MaxInstances
+	}
 	app.EnableTrial = req.EnableTrial
-	app.TrialBalance = req.TrialBalance
-	app.TrialDays = req.TrialDays
+	if req.TrialBalance > 0 {
+		app.TrialBalance = req.TrialBalance
+	}
+	if req.TrialDays > 0 {
+		app.TrialDays = req.TrialDays
+	}
 	app.EnableFreePeriod = req.EnableFreePeriod
-	app.FreePeriodType = req.FreePeriodType
+	if req.FreePeriodType != "" {
+		app.FreePeriodType = req.FreePeriodType
+	}
 	app.FreePeriodStart = req.FreePeriodStart
 	app.FreePeriodEnd = req.FreePeriodEnd
 	app.FreePeriodWeekdays = req.FreePeriodWeekdays
@@ -409,12 +439,24 @@ func handleUpdateApplication(c *gin.Context) {
 	if req.LockDuration > 0 {
 		app.LockDuration = req.LockDuration
 	}
-	app.Status = req.Status
-	app.DeductionMode = req.DeductionMode
-	app.DeductionType = req.DeductionType
-	app.DeductionInterval = req.DeductionInterval
-	app.DeductionUnit = req.DeductionUnit
-	app.DeductionAmount = req.DeductionAmount
+	if req.Status != "" {
+		app.Status = req.Status
+	}
+	if req.DeductionMode != "" {
+		app.DeductionMode = req.DeductionMode
+	}
+	if req.DeductionType != "" {
+		app.DeductionType = req.DeductionType
+	}
+	if req.DeductionInterval > 0 {
+		app.DeductionInterval = req.DeductionInterval
+	}
+	if req.DeductionUnit != "" {
+		app.DeductionUnit = req.DeductionUnit
+	}
+	if req.DeductionAmount > 0 {
+		app.DeductionAmount = req.DeductionAmount
+	}
 	app.EnablePasswordReset = req.EnablePasswordReset
 	if req.PasswordResetMethod != "" {
 		app.PasswordResetMethod = req.PasswordResetMethod