revert: remove fork-only changes from release sync

Revert payment/wechat, sora/claude-max cleanup, fork-only migrations,
and cosmetic changes that were brought in by the release sync commit.
Keep only channel-monitor related improvements:
- PublicSettingsInjectionPayload named struct with drift test
- ChannelMonitorRunner graceful shutdown in wire
- image_output_price in SupportedModelChip
- Simplified buildSelfNavItems in AppSidebar
- Gateway WARN logs for 503 branches

backend/internal/service/pricing_service.go

@@ -812,6 +812,16 @@ func (s *PricingService) matchOpenAIModel(model string) *LiteLLMModelPricing {
 		return openAIGPT54FallbackPricing
 	}
 
+	if isOpenAIImageGenerationModel(model) {
+		for _, candidate := range []string{"gpt-image-2", "gpt-image-1.5", "gpt-image-1"} {
+			if pricing, ok := s.pricingData[candidate]; ok {
+				logger.LegacyPrintf("service.pricing", "[Pricing] OpenAI image fallback matched %s -> %s", model, candidate)
+				return pricing
+			}
+		}
+		return nil
+	}
+
 	// 最终回退到 DefaultTestModel
 	defaultModel := strings.ToLower(openai.DefaultTestModel)
 	if pricing, ok := s.pricingData[defaultModel]; ok {