sync: bring over remaining release/custom-0.1.115 changes

- Extract PublicSettingsInjectionPayload named struct with drift test
- Add channel_monitor_default_interval_seconds to SSR injection
- Add image_output_price to SupportedModelChip
- Simplify AppSidebar buildSelfNavItems (admins see available channels)
- Add gateway WARN logs for 503 no-available-accounts branches
- Wire ChannelMonitorRunner into provideCleanup for graceful shutdown
- Add migrations 130/131 (CC template userid fix + mimicry field cleanup)
- Clean up fork-only features (sora, claude max simulation, client affinity)
- Remove ~320 obsolete i18n keys
- Add codexUsage utility, WechatServiceButton, BulkEditAccountModal
- Tidy go.sum

backend/internal/service/pricing_service_test.go

@@ -128,21 +128,6 @@ func TestGetModelPricing_Gpt54NanoUsesDedicatedStaticFallbackWhenRemoteMissing(t
 	require.Zero(t, got.LongContextInputTokenThreshold)
 }
 
-func TestGetModelPricing_ImageModelDoesNotFallbackToTextModel(t *testing.T) {
-	imagePricing := &LiteLLMModelPricing{InputCostPerToken: 3}
-	textPricing := &LiteLLMModelPricing{InputCostPerToken: 9}
-
-	svc := &PricingService{
-		pricingData: map[string]*LiteLLMModelPricing{
-			"gpt-image-2": imagePricing,
-			"gpt-5.4":     textPricing,
-		},
-	}
-
-	got := svc.GetModelPricing("gpt-image-3")
-	require.Same(t, imagePricing, got)
-}
-
 func TestParsePricingData_PreservesPriorityAndServiceTierFields(t *testing.T) {
 	raw := map[string]any{
 		"gpt-5.4": map[string]any{