Debug: show API base URL on login page

frontend/src/api.ts

@@ -24,6 +24,10 @@ const frontendEnv = (import.meta as ImportMeta & {
 const configuredApiUrl = frontendEnv?.VITE_API_URL?.trim()?.replace(/\/$/, "");
 const API_BASE_URL = configuredApiUrl || window.location.origin;
 
+export function getApiBaseUrl(): string {
+  return API_BASE_URL;
+}
+
 if (!configuredApiUrl) {
   console.error(
     "[api] Missing required VITE_API_URL. Falling back to same-origin requests. " +
@@ -160,6 +164,9 @@ export async function login(
   email: string,
   password: string,
 ): Promise<LoginResponse> {
+  const loginUrl = buildApiUrl("/auth/login");
+  console.log("[auth] Login URL:", loginUrl);
+
   return request<LoginResponse>("/auth/login", {
     method: "POST",
     body: JSON.stringify({ email, password }),

frontend/src/components/LoginPanel.tsx

@@ -1,5 +1,5 @@
 import { FormEvent, useState } from "react";
-import { login } from "../api";
+import { getApiBaseUrl, login } from "../api";
 import Banner from "./ui/Banner";
 import Button from "./ui/Button";
 import Card from "./ui/Card";
@@ -14,6 +14,7 @@ export default function LoginPanel({ onToken }: LoginPanelProps): JSX.Element {
   const [password, setPassword] = useState("user123");
   const [error, setError] = useState<string | null>(null);
   const [isSubmitting, setIsSubmitting] = useState(false);
+  const apiBaseUrl = getApiBaseUrl();
 
   async function handleSubmit(
     event: FormEvent<HTMLFormElement>,
@@ -57,6 +58,7 @@ export default function LoginPanel({ onToken }: LoginPanelProps): JSX.Element {
         <Button type="submit" disabled={isSubmitting}>
           {isSubmitting ? "Signing in…" : "Sign in"}
         </Button>
+        <small className="login-api-debug">API: {apiBaseUrl}</small>
       </form>
 
       {error ? <Banner tone="error" message={error} /> : null}

frontend/src/styles.css

@@ -48,3 +48,10 @@ th, td { text-align: left; border-bottom: 1px solid #d8dee4; padding: 8px; font-
 
 .toast { position: fixed; bottom: 16px; right: 16px; background: #1f883d; color: #fff; padding: 10px 14px; border-radius: 8px; }
 .error-boundary-fallback { margin: 40px auto; max-width: 640px; background: #fff; border: 1px solid #d0d7de; padding: 20px; border-radius: 8px; }
+
+.login-api-debug {
+  display: block;
+  margin-top: 8px;
+  color: #57606a;
+  font-size: 12px;
+}