build(docker): add runtime-configured frontend image

frontend/src/api/runtime-config.ts

@@ -0,0 +1,17 @@
+export interface RuntimeConfig {
+  backendBaseUrl?: string;
+}
+
+declare global {
+  interface Window {
+    __THOTHII_CONFIG__?: RuntimeConfig;
+  }
+}
+
+export function resolveBackendUrl(config: RuntimeConfig | undefined): string {
+  return config?.backendBaseUrl ?? import.meta.env.VITE_BACKEND_URL ?? "";
+}
+
+export const backendBaseUrl =
+  resolveBackendUrl(typeof window === "undefined" ? undefined : window.__THOTHII_CONFIG__) ||
+  "http://localhost:8787";