flatten app to repo root and update docker deployment for single-stack runtime

lib/runtime-url.ts

@@ -0,0 +1,13 @@
+function trimTrailingSlash(value: string) {
+  return value.endsWith('/') ? value.slice(0, -1) : value;
+}
+
+export function resolveApiBaseURL(configuredBaseURL: string | undefined) {
+  const candidate = configuredBaseURL?.trim();
+
+  if (!candidate) {
+    return '';
+  }
+
+  return trimTrailingSlash(candidate);
+}