Wallet与Withdrawal模块：完成分字段重构

核心改造：
1. Wallet模块DTO层全部改为*Cent int64字段
2. Wallet.Entry结构从Amount float64改为AmountCent int64
3. Repository层applyEntry函数使用整数加减，无需浮点运算
4. Withdrawal模块DTO/Request全部改为*Cent字段
5. 所有wallet.AppendEntries调用点改为AmountCent
6. 提现手续费计算改为分单位

技术细节：
- 删除了roundWalletMoney函数（不再需要）
- toAccountDTO/toLedgerDTO使用*Cent字段
- 最小提现金额：10元=1000分
- 最大提现金额：5000元=500000分
- 编译验证通过 ✅

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/internal/modules/withdrawal/repository.go

@@ -39,9 +39,9 @@ func (r *Repository) Create(userID uint64, req CreateWithdrawalRequest) (*Withdr
 		return nil, err
 	}
 
-	// 计算手续费和实际到账金额
-	fee := req.Amount * WithdrawalFeeRate
-	actualAmount := req.Amount - fee
+	// 计算手续费和实际到账金额（分）
+	feeCent := int64(float64(req.AmountCent) * WithdrawalFeeRate)
+	actualAmountCent := req.AmountCent - feeCent
 
 	// 生成提现单号
 	withdrawNo, err := generateWithdrawNo()
@@ -58,9 +58,9 @@ func (r *Repository) Create(userID uint64, req CreateWithdrawalRequest) (*Withdr
 	withdrawal := model.WithdrawalRequest{
 		WithdrawNo:       withdrawNo,
 		UserID:           userID,
-		Amount:           req.Amount,
-		Fee:              fee,
-		ActualAmount:     actualAmount,
+		AmountCent:       req.AmountCent,
+		FeeCent:          feeCent,
+		ActualAmountCent: actualAmountCent,
 		PaymentAccountID: &req.PaymentAccountID,
 		AccountType:      paymentAccount.AccountType,
 		AccountName:      paymentAccount.AccountName,
@@ -81,7 +81,7 @@ func (r *Repository) Create(userID uint64, req CreateWithdrawalRequest) (*Withdr
 		if err := wallet.AppendEntries(tx, wallet.Entry{
 			UserID:      userID,
 			Direction:   "out",
-			Amount:      req.Amount,
+			AmountCent:  req.AmountCent,
 			BalanceType: "available",
 			BizType:     "withdraw_freeze",
 			BizNo:       withdrawNo,
@@ -89,7 +89,7 @@ func (r *Repository) Create(userID uint64, req CreateWithdrawalRequest) (*Withdr
 		}, wallet.Entry{
 			UserID:      userID,
 			Direction:   "in",
-			Amount:      req.Amount,
+			AmountCent:  req.AmountCent,
 			BalanceType: "frozen",
 			BizType:     "withdraw_freeze",
 			BizNo:       withdrawNo,
@@ -179,7 +179,7 @@ func (r *Repository) Cancel(userID, id uint64) error {
 		if err := wallet.AppendEntries(tx, wallet.Entry{
 			UserID:      userID,
 			Direction:   "out",
-			Amount:      withdrawal.Amount,
+			AmountCent:  withdrawal.AmountCent,
 			BalanceType: "frozen",
 			BizType:     "withdraw_cancel",
 			BizNo:       withdrawal.WithdrawNo,
@@ -187,7 +187,7 @@ func (r *Repository) Cancel(userID, id uint64) error {
 		}, wallet.Entry{
 			UserID:      userID,
 			Direction:   "in",
-			Amount:      withdrawal.Amount,
+			AmountCent:  withdrawal.AmountCent,
 			BalanceType: "available",
 			BizType:     "withdraw_cancel",
 			BizNo:       withdrawal.WithdrawNo,
@@ -292,7 +292,7 @@ func (r *Repository) Review(adminID, id uint64, req ReviewWithdrawalRequest) (*W
 			if err := wallet.AppendEntries(tx, wallet.Entry{
 				UserID:      withdrawal.UserID,
 				Direction:   "out",
-				Amount:      withdrawal.Amount,
+				AmountCent:  withdrawal.AmountCent,
 				BalanceType: "frozen",
 				BizType:     "withdraw_reject",
 				BizNo:       withdrawal.WithdrawNo,
@@ -300,7 +300,7 @@ func (r *Repository) Review(adminID, id uint64, req ReviewWithdrawalRequest) (*W
 			}, wallet.Entry{
 				UserID:      withdrawal.UserID,
 				Direction:   "in",
-				Amount:      withdrawal.Amount,
+				AmountCent:  withdrawal.AmountCent,
 				BalanceType: "available",
 				BizType:     "withdraw_reject",
 				BizNo:       withdrawal.WithdrawNo,
@@ -351,7 +351,7 @@ func (r *Repository) ConfirmPayment(adminID, id uint64, req ConfirmPaymentReques
 		if err := wallet.AppendEntries(tx, wallet.Entry{
 			UserID:      withdrawal.UserID,
 			Direction:   "out",
-			Amount:      withdrawal.Amount,
+			AmountCent:  withdrawal.AmountCent,
 			BalanceType: "frozen",
 			BizType:     "withdraw_complete",
 			BizNo:       withdrawal.WithdrawNo,
@@ -373,22 +373,22 @@ func (r *Repository) ConfirmPayment(adminID, id uint64, req ConfirmPaymentReques
 // 转换为用户DTO
 func toDTO(w model.WithdrawalRequest) WithdrawalDTO {
 	return WithdrawalDTO{
-		ID:           w.ID,
-		WithdrawNo:   w.WithdrawNo,
-		UserID:       w.UserID,
-		Amount:       w.Amount,
-		Fee:          w.Fee,
-		ActualAmount: w.ActualAmount,
-		AccountType:  w.AccountType,
-		AccountName:  w.AccountName,
-		AccountNo:    w.AccountNo,
-		BankName:     w.BankName,
-		Status:       w.Status,
-		ReviewRemark: w.ReviewRemark,
-		CreatedAt:    w.CreatedAt,
-		UpdatedAt:    w.UpdatedAt,
-		ReviewedAt:   w.ReviewedAt,
-		PaidAt:       w.PaidAt,
+		ID:               w.ID,
+		WithdrawNo:       w.WithdrawNo,
+		UserID:           w.UserID,
+		AmountCent:       w.AmountCent,
+		FeeCent:          w.FeeCent,
+		ActualAmountCent: w.ActualAmountCent,
+		AccountType:      w.AccountType,
+		AccountName:      w.AccountName,
+		AccountNo:        w.AccountNo,
+		BankName:         w.BankName,
+		Status:           w.Status,
+		ReviewRemark:     w.ReviewRemark,
+		CreatedAt:        w.CreatedAt,
+		UpdatedAt:        w.UpdatedAt,
+		ReviewedAt:       w.ReviewedAt,
+		PaidAt:           w.PaidAt,
 	}
 }
 
@@ -440,9 +440,9 @@ func (r *Repository) toDetailDTO(w model.WithdrawalRequest) (*WithdrawalDetailDT
 		UserID:           w.UserID,
 		UserNickname:     user.Nickname,
 		UserPhone:        user.Phone,
-		Amount:           w.Amount,
-		Fee:              w.Fee,
-		ActualAmount:     w.ActualAmount,
+		AmountCent:       w.AmountCent,
+		FeeCent:          w.FeeCent,
+		ActualAmountCent: w.ActualAmountCent,
 		PaymentAccountID: w.PaymentAccountID,
 		AccountType:      w.AccountType,
 		AccountName:      w.AccountName,