Reapply "Add Turnstile captcha to login"

This reverts commit a7c732e139.

src/dataService.ts

@@ -55,27 +55,30 @@ const buildDateRangeParams = (dateRange: DateRange) => new URLSearchParams({
     end: formatDateParam(dateRange.end)
 });
 
-export const login = async (email: string, password: string): Promise<boolean> => {
+export type LoginResult = 'success' | 'invalid_credentials' | 'captcha_failed' | 'server_error';
+
+export const login = async (email: string, password: string, captchaToken?: string): Promise<LoginResult> => {
   try {
     const response = await fetch(`${API_URL}/login`, {
       method: 'POST',
       headers: {
         'Content-Type': 'application/json',
       },
-      body: JSON.stringify({ email, password }),
+      body: JSON.stringify({ email, password, captchaToken }),
     });
 
     if (response.ok) {
       const data = await response.json() as { token?: string; user?: AuthUser };
-      if (!data.token || !data.user) return false;
+      if (!data.token || !data.user) return 'server_error';
       localStorage.setItem('auth_token', data.token);
       localStorage.setItem('auth_user', JSON.stringify(data.user));
-      return true;
+      return 'success';
     }
-    return false;
+    if (response.status === 403) return 'captcha_failed';
+    return 'invalid_credentials';
   } catch (error) {
     console.error('Login failed', error);
-    return false;
+    return 'server_error';
   }
 };