feat(web): I1 shell and I2 customer/project UI

Vue 3 + Element Plus layout with JWT login, RBAC routes, axios 401
handling with token restore, and Customers/Projects views wired to
platform APIs.

Made-with: Cursor

web/delivery-platform-ui/src/utils/apiErrorMessage.js

@@ -0,0 +1,19 @@
+/**
+ * @param {unknown} err
+ * @param {string} fallback
+ */
+export function apiErrorMessage(err, fallback) {
+  const e = err && typeof err === "object" && "response" in err ? err : null;
+  const data = e?.response?.data;
+  if (typeof data === "string" && data.trim()) return data;
+  if (data && typeof data === "object") {
+    if (typeof data.message === "string" && data.message.trim()) return data.message;
+    if (Array.isArray(data.errors)) {
+      const parts = data.errors
+        .map((x) => (x && typeof x === "object" ? x.defaultMessage || x.message : null))
+        .filter(Boolean);
+      if (parts.length) return parts.join("；");
+    }
+  }
+  return fallback;
+}