feat(affiliate): 完善邀请返利系统

- 修复返利不到账的根因：tryClaimAffiliateRebateAudit 中 PostgreSQL 参数类型推断冲突
  - 补全 OAuth 注册路径（LinuxDo/OIDC/WeChat/Pending Flow）的邀请码绑定
  - 前端 OAuth 注册页面传递 aff_code 参数
  - 新增返利冻结期机制：可配置冻结时间，到期后自动解冻（懒解冻）
  - 新增返利有效期：绑定后 N 天内有效，过期不再产生返利
  - 新增单人返利上限：超出上限部分精确截断
  - 增强返利流程 slog 结构化日志，便于排查问题
  - 已邀请用户列表增加返利明细列

backend/internal/service/setting_service.go

@@ -1175,6 +1175,24 @@ func (s *SettingService) buildSystemSettingsUpdates(ctx context.Context, setting
 	updates[SettingKeyDefaultBalance] = strconv.FormatFloat(settings.DefaultBalance, 'f', 8, 64)
 	settings.AffiliateRebateRate = clampAffiliateRebateRate(settings.AffiliateRebateRate)
 	updates[SettingKeyAffiliateRebateRate] = strconv.FormatFloat(settings.AffiliateRebateRate, 'f', 8, 64)
+	if settings.AffiliateRebateFreezeHours < 0 {
+		settings.AffiliateRebateFreezeHours = AffiliateRebateFreezeHoursDefault
+	}
+	if settings.AffiliateRebateFreezeHours > AffiliateRebateFreezeHoursMax {
+		settings.AffiliateRebateFreezeHours = AffiliateRebateFreezeHoursMax
+	}
+	updates[SettingKeyAffiliateRebateFreezeHours] = strconv.Itoa(settings.AffiliateRebateFreezeHours)
+	if settings.AffiliateRebateDurationDays < 0 {
+		settings.AffiliateRebateDurationDays = AffiliateRebateDurationDaysDefault
+	}
+	if settings.AffiliateRebateDurationDays > AffiliateRebateDurationDaysMax {
+		settings.AffiliateRebateDurationDays = AffiliateRebateDurationDaysMax
+	}
+	updates[SettingKeyAffiliateRebateDurationDays] = strconv.Itoa(settings.AffiliateRebateDurationDays)
+	if settings.AffiliateRebatePerInviteeCap < 0 {
+		settings.AffiliateRebatePerInviteeCap = AffiliateRebatePerInviteeCapDefault
+	}
+	updates[SettingKeyAffiliateRebatePerInviteeCap] = strconv.FormatFloat(settings.AffiliateRebatePerInviteeCap, 'f', 8, 64)
 	updates[SettingKeyDefaultUserRPMLimit] = strconv.Itoa(settings.DefaultUserRPMLimit)
 	defaultSubsJSON, err := json.Marshal(settings.DefaultSubscriptions)
 	if err != nil {
@@ -1512,6 +1530,54 @@ func (s *SettingService) GetAffiliateRebateRatePercent(ctx context.Context) floa
 	return clampAffiliateRebateRate(rate)
 }
 
+// GetAffiliateRebateFreezeHours 返回返利冻结期（小时）。
+// 返回 0 表示不冻结（向后兼容）。
+func (s *SettingService) GetAffiliateRebateFreezeHours(ctx context.Context) int {
+	raw, err := s.settingRepo.GetValue(ctx, SettingKeyAffiliateRebateFreezeHours)
+	if err != nil {
+		return AffiliateRebateFreezeHoursDefault
+	}
+	hours, err := strconv.Atoi(strings.TrimSpace(raw))
+	if err != nil || hours < 0 {
+		return AffiliateRebateFreezeHoursDefault
+	}
+	if hours > AffiliateRebateFreezeHoursMax {
+		return AffiliateRebateFreezeHoursMax
+	}
+	return hours
+}
+
+// GetAffiliateRebateDurationDays 返回返利有效期（天）。
+// 返回 0 表示永久有效。
+func (s *SettingService) GetAffiliateRebateDurationDays(ctx context.Context) int {
+	raw, err := s.settingRepo.GetValue(ctx, SettingKeyAffiliateRebateDurationDays)
+	if err != nil {
+		return AffiliateRebateDurationDaysDefault
+	}
+	days, err := strconv.Atoi(strings.TrimSpace(raw))
+	if err != nil || days < 0 {
+		return AffiliateRebateDurationDaysDefault
+	}
+	if days > AffiliateRebateDurationDaysMax {
+		return AffiliateRebateDurationDaysMax
+	}
+	return days
+}
+
+// GetAffiliateRebatePerInviteeCap 返回单人返利上限。
+// 返回 0 表示无上限。
+func (s *SettingService) GetAffiliateRebatePerInviteeCap(ctx context.Context) float64 {
+	raw, err := s.settingRepo.GetValue(ctx, SettingKeyAffiliateRebatePerInviteeCap)
+	if err != nil {
+		return AffiliateRebatePerInviteeCapDefault
+	}
+	cap, err := strconv.ParseFloat(strings.TrimSpace(raw), 64)
+	if err != nil || cap < 0 || math.IsNaN(cap) || math.IsInf(cap, 0) {
+		return AffiliateRebatePerInviteeCapDefault
+	}
+	return cap
+}
+
 // IsPasswordResetEnabled 检查是否启用密码重置功能
 // 要求：必须同时开启邮件验证
 func (s *SettingService) IsPasswordResetEnabled(ctx context.Context) bool {
@@ -1755,6 +1821,9 @@ func (s *SettingService) InitializeDefaultSettings(ctx context.Context) error {
 		SettingKeyDefaultConcurrency:                       strconv.Itoa(s.cfg.Default.UserConcurrency),
 		SettingKeyDefaultBalance:                           strconv.FormatFloat(s.cfg.Default.UserBalance, 'f', 8, 64),
 		SettingKeyAffiliateRebateRate:                      strconv.FormatFloat(AffiliateRebateRateDefault, 'f', 8, 64),
+		SettingKeyAffiliateRebateFreezeHours:               strconv.Itoa(AffiliateRebateFreezeHoursDefault),
+		SettingKeyAffiliateRebateDurationDays:              strconv.Itoa(AffiliateRebateDurationDaysDefault),
+		SettingKeyAffiliateRebatePerInviteeCap:             strconv.FormatFloat(AffiliateRebatePerInviteeCapDefault, 'f', 2, 64),
 		SettingKeyDefaultUserRPMLimit:                      "0",
 		SettingKeyDefaultSubscriptions:                     "[]",
 		SettingKeyAuthSourceDefaultEmailBalance:            "0",
@@ -1890,6 +1959,21 @@ func (s *SettingService) parseSettings(settings map[string]string) *SystemSettin
 	} else {
 		result.AffiliateRebateRate = AffiliateRebateRateDefault
 	}
+	if freezeHours, err := strconv.Atoi(settings[SettingKeyAffiliateRebateFreezeHours]); err == nil && freezeHours >= 0 {
+		if freezeHours > AffiliateRebateFreezeHoursMax {
+			freezeHours = AffiliateRebateFreezeHoursMax
+		}
+		result.AffiliateRebateFreezeHours = freezeHours
+	}
+	if durationDays, err := strconv.Atoi(settings[SettingKeyAffiliateRebateDurationDays]); err == nil && durationDays >= 0 {
+		if durationDays > AffiliateRebateDurationDaysMax {
+			durationDays = AffiliateRebateDurationDaysMax
+		}
+		result.AffiliateRebateDurationDays = durationDays
+	}
+	if perInviteeCap, err := strconv.ParseFloat(settings[SettingKeyAffiliateRebatePerInviteeCap], 64); err == nil && perInviteeCap >= 0 {
+		result.AffiliateRebatePerInviteeCap = perInviteeCap
+	}
 	result.DefaultSubscriptions = parseDefaultSubscriptions(settings[SettingKeyDefaultSubscriptions])
 
 	// 敏感信息直接返回，方便测试连接时使用