Fix client base path handling via explicit meta

wwwroot/js/api.js

@@ -1,13 +1,15 @@
 const defaultHeaders = { "Content-Type": "application/json" };
 
-const metaBase = document.querySelector('meta[name="app-base"]')?.content || "";
-const autoBase = (() => {
-  const parts = window.location.pathname.split("/").filter(Boolean);
-  return parts.length ? `/${parts[0]}` : "";
-})();
-const basePath = metaBase || autoBase;
+const rawBase = document.querySelector('meta[name="app-base"]')?.content || "";
+const basePath = normalizeBase(rawBase);
 const withBase = (path) => `${basePath}${path}`;
 
+function normalizeBase(value) {
+  if (!value) return "";
+  if (!value.startsWith("/")) return `/${value}`;
+  return value.endsWith("/") ? value.slice(0, -1) : value;
+}
+
 async function request(path, { method = "GET", body } = {}) {
   const res = await fetch(withBase(path), {
     method,