add a CLIENT_CONFIG to the client, serve from BE with env vars

client/src/Utils/runtimeConfig.ts

@@ -0,0 +1,18 @@
+import type { LogLevel } from "@/Types/Log";
+
+// Served by GET /config.js (rendered from server env) or a static config.js
+// next to index.html; loaded before the bundle in index.html.
+export interface RuntimeConfig {
+	apiBaseUrl?: string;
+	clientHost?: string;
+	logLevel?: LogLevel;
+}
+
+declare global {
+	interface Window {
+		__CHECKMATE_CONFIG__?: RuntimeConfig;
+	}
+}
+
+export const runtimeConfig: RuntimeConfig =
+	(typeof window !== "undefined" && window.__CHECKMATE_CONFIG__) || {};