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/openai_account_scheduler.go

@@ -781,7 +781,7 @@ func (s *defaultOpenAIAccountScheduler) isAccountRequestCompatible(account *Acco
 	if account == nil {
 		return false
 	}
-	if req.RequestedModel != "" && !account.IsOpenAIPassthroughEnabled() && !account.IsModelSupported(req.RequestedModel) {
+	if req.RequestedModel != "" && !account.IsModelSupported(req.RequestedModel) {
 		return false
 	}
 	return account.SupportsOpenAIImageCapability(req.RequiredImageCapability)