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/gateway_multiplatform_test.go

@@ -82,6 +82,10 @@ func (m *mockAccountRepoForPlatform) FindByExtraField(ctx context.Context, key s
 	return nil, nil
 }
 
+func (m *mockAccountRepoForPlatform) CountByTLSFingerprintProfile(ctx context.Context) (map[int64]int, error) {
+	return nil, nil
+}
+
 func (m *mockAccountRepoForPlatform) ListCRSAccountIDs(ctx context.Context) (map[string]int64, error) {
 	return nil, nil
 }