fix: resolve cherry-pick conflicts and restore compilation

- Restore gateway_cache.go to upstream (no lua embeds)
- Restore payment_order.go to upstream (use out_trade_no lookup)
- Restore payment_fulfillment.go to upstream (same reason)
- Add FeaturesConfig field and IsWebSearchEmulationEnabled to Channel
- Add applyAccountStatsCost wrapper function
- Add SettingKeyWebSearchEmulationConfig constant
- Add WebSearchEmulationEnabled to SystemSettings
- Add notify code rate limiting methods to EmailCache interface
- Remove AllowUserRefund references (ent schema not present)
- Fix duplicate import in payment_handler.go
- Fix wire_gen.go argument mismatches

backend/internal/service/channel.go

@@ -39,7 +39,8 @@ type Channel struct {
 	Status             string
 	BillingModelSource string // "requested", "upstream", or "channel_mapped"
 	RestrictModels     bool   // 是否限制模型（仅允许定价列表中的模型）
-	Features           string // 渠道特性描述（JSON 数组），用于支付页面展示
+	Features           string         // 渠道特性描述（JSON 数组），用于支付页面展示
+	FeaturesConfig     map[string]any // 渠道功能配置（如 web search emulation）
 	CreatedAt          time.Time
 	UpdatedAt          time.Time
 
@@ -222,6 +223,19 @@ func (c *Channel) Clone() *Channel {
 	return &cp
 }
 
+// IsWebSearchEmulationEnabled 返回该渠道是否为指定平台启用了 web search 模拟。
+func (c *Channel) IsWebSearchEmulationEnabled(platform string) bool {
+	if c == nil || c.FeaturesConfig == nil {
+		return false
+	}
+	wse, ok := c.FeaturesConfig[featureKeyWebSearchEmulation].(map[string]any)
+	if !ok {
+		return false
+	}
+	enabled, ok := wse[platform].(bool)
+	return ok && enabled
+}
+
 // deepCopyFeaturesConfig creates a deep copy of FeaturesConfig to prevent cache pollution.
 func deepCopyFeaturesConfig(src map[string]any) map[string]any {
 	dst := make(map[string]any, len(src))