fix: auto-login after checkout, ThankYou guest buttons, forgot password page

1. Auto-login after checkout:
   - Added wp_set_auth_cookie() and wp_set_current_user() in CheckoutController
   - Auto-registered users are now logged in when thank-you page loads

2. ThankYou page guest buttons:
   - Added 'Login / Create Account' button for guests
   - Shows for both receipt and basic templates
   - No more dead-end after placing order as guest

3. Forgot password flow:
   - Created ForgotPassword page component (/forgot-password route)
   - Added forgot_password API endpoint in AuthController
   - Uses WordPress retrieve_password() for reset email
   - Replaced wp-login.php link in Login page

includes/Api/CheckoutController.php

@@ -300,6 +300,10 @@ class CheckoutController {
                         // The real password is already set via wp_insert_user
                         update_user_meta($new_user_id, '_woonoow_temp_password', $password);
                         
+                        // AUTO-LOGIN: Set authentication cookie so user is logged in after page reload
+                        wp_set_auth_cookie($new_user_id, true);
+                        wp_set_current_user($new_user_id);
+                        
                         // Set WooCommerce customer billing data
                         $customer = new \WC_Customer($new_user_id);