fix(subscription): round remaining days up

backend/internal/service/subscription_calculate_progress_test.go

@@ -34,7 +34,7 @@ func TestCalculateProgress_BasicFields(t *testing.T) {
 	assert.Equal(t, int64(100), progress.ID)
 	assert.Equal(t, "Premium", progress.GroupName)
 	assert.Equal(t, sub.ExpiresAt, progress.ExpiresAt)
-	assert.True(t, progress.ExpiresInDays == 29 || progress.ExpiresInDays == 30, "ExpiresInDays should be 29 or 30, got %d", progress.ExpiresInDays)
+	assert.Equal(t, 30, progress.ExpiresInDays)
 	assert.Nil(t, progress.Daily, "无日限额时 Daily 应为 nil")
 	assert.Nil(t, progress.Weekly, "无周限额时 Weekly 应为 nil")
 	assert.Nil(t, progress.Monthly, "无月限额时 Monthly 应为 nil")

backend/internal/service/user_subscription.go

@@ -2,6 +2,8 @@ package service
 
 import "time"
 
+const subscriptionDayDuration = 24 * time.Hour
+
 type UserSubscription struct {
 	ID      int64
 	UserID  int64
@@ -41,10 +43,20 @@ func (s *UserSubscription) IsExpired() bool {
 }
 
 func (s *UserSubscription) DaysRemaining() int {
-	if s.IsExpired() {
+	return s.daysRemainingAt(time.Now())
+}
+
+func (s *UserSubscription) daysRemainingAt(now time.Time) int {
+	remaining := s.ExpiresAt.Sub(now)
+	if remaining <= 0 {
 		return 0
 	}
-	return int(time.Until(s.ExpiresAt).Hours() / 24)
+
+	days := int(remaining / subscriptionDayDuration)
+	if remaining%subscriptionDayDuration != 0 {
+		days++
+	}
+	return days
 }
 
 func (s *UserSubscription) IsWindowActivated() bool {

backend/internal/service/user_subscription_days_remaining_test.go

@@ -0,0 +1,37 @@
+//go:build unit
+
+package service
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUserSubscriptionDaysRemainingAt(t *testing.T) {
+	now := time.Date(2026, time.July, 19, 12, 0, 0, 0, time.UTC)
+	tests := []struct {
+		name      string
+		expiresAt time.Time
+		want      int
+	}{
+		{name: "expired", expiresAt: now.Add(-time.Nanosecond), want: 0},
+		{name: "expires now", expiresAt: now, want: 0},
+		{name: "less than one day", expiresAt: now.Add(subscriptionDayDuration - time.Nanosecond), want: 1},
+		{name: "exactly one day", expiresAt: now.Add(subscriptionDayDuration), want: 1},
+		{name: "over one day", expiresAt: now.Add(subscriptionDayDuration + time.Nanosecond), want: 2},
+		{name: "less than two days", expiresAt: now.Add(2*subscriptionDayDuration - time.Nanosecond), want: 2},
+		{name: "exactly two days", expiresAt: now.Add(2 * subscriptionDayDuration), want: 2},
+		{name: "over two days", expiresAt: now.Add(2*subscriptionDayDuration + time.Nanosecond), want: 3},
+		{name: "exactly seven days", expiresAt: now.Add(7 * subscriptionDayDuration), want: 7},
+		{name: "over seven days", expiresAt: now.Add(7*subscriptionDayDuration + time.Nanosecond), want: 8},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			sub := &UserSubscription{ExpiresAt: tt.expiresAt}
+			require.Equal(t, tt.want, sub.daysRemainingAt(now))
+		})
+	}
+}