fix(app): read instance theme color without an active runtime (#3391)

fluxer_app/src/app/App.tsx

@@ -22,6 +22,7 @@ import {useTabKeyFocusGuard} from '@app/features/app/hooks/useTabKeyFocusGuard';
 import {type LayoutVariant, LayoutVariantProvider} from '@app/features/app/state/LayoutVariantContext';
 import RuntimeConfig from '@app/features/app/state/RuntimeConfig';
 import RuntimeCrash from '@app/features/app/state/RuntimeCrash';
+import DeveloperOptions from '@app/features/devtools/state/DeveloperOptions';
 import {showMyselfTypingHelper} from '@app/features/devtools/utils/ShowMyselfTypingHelper';
 import GatewayConnection from '@app/features/gateway/transport/GatewayConnection';
 import GatewaySessions from '@app/features/gateway/transport/GatewaySessionPool';
@@ -83,6 +84,14 @@ interface AppWrapperProps {
 	children: ReactNode;
 }
 
+function getInstanceThemeColor(): string | null {
+	const snapshot = RuntimeConfig.getSnapshotOrNull();
+	if (snapshot === null || !(DeveloperOptions.selfHostedModeOverride || snapshot.features.self_hosted)) {
+		return null;
+	}
+	return snapshot.appPublic.branding.theme_color ?? null;
+}
+
 export const AppWrapper = observer(({children}: AppWrapperProps) => {
 	const {i18n} = useLingui();
 	const reducedMotion = Accessibility.useReducedMotion;
@@ -191,9 +200,7 @@ export const AppWrapper = observer(({children}: AppWrapperProps) => {
 		messageGutter: Accessibility.messageGutter,
 		messageGroupSpacing: Accessibility.getMessageGroupSpacingValue(messageDisplayCompact),
 		hdrDisplayMode: Accessibility.hdrDisplayMode,
-		instanceThemeColor: RuntimeConfig.isSelfHosted()
-			? (RuntimeConfig.getSnapshotOrNull()?.appPublic.branding.theme_color ?? null)
-			: null,
+		instanceThemeColor: getInstanceThemeColor(),
 	});
 	useCustomThemeStyle({
 		enabledThemeCss: ThemeLibrary.activeThemeCss,