feat(invite-code): one-time invite codes with rewards, usage log, import/export

- 一次性邀请码：批量生成（次数/有效期/备注/四类奖励）、原子消费防超发、
  开启注册验证时奖励延迟发放（账本幂等键）
- Zibll 兼容文本导入（points/balance/vip/vip_time/level_integral，分隔符可自定义，
  第三段标识存为备注）、CSV 全字段导出与可回流文本导出
- 使用记录表 aksrt_invite_code_usage + 后台使用者列；注册表单 400ms 防抖实时校验
- 注册门控三模式（close/open/must）设置链路（PHP schema + admin SPA schema）
- 契约测试覆盖建表/消费竞态/导入导出/备注全链路

templates/parts/auth-content.php

@@ -34,6 +34,9 @@ $referral = $settings ? $settings::get_referral_registration_settings() : ['enab
 $ref_mode = !empty($referral['enabled']) ? (string) ($referral['register_field'] ?? 'hidden') : 'hidden';
 $ref_hint = $ref_mode === 'required' ? (string) ($referral['required_desc'] ?? '') : (string) ($referral['open_desc'] ?? '');
 $ref_value = !empty($_GET['ref']) ? sanitize_key(wp_unslash((string) $_GET['ref'])) : (!empty($_COOKIE['aksrt_referral']) ? sanitize_key(wp_unslash((string) $_COOKIE['aksrt_referral'])) : '');
+$invite_code_settings = $settings ? $settings::get_invite_code_registration_settings() : ['enabled' => false, 'register_field' => 'hidden', 'open_desc' => '', 'required_desc' => ''];
+$invite_mode = !empty($invite_code_settings['enabled']) ? (string) ($invite_code_settings['register_field'] ?? 'hidden') : 'hidden';
+$invite_hint = $invite_mode === 'required' ? (string) ($invite_code_settings['required_desc'] ?? '') : (string) ($invite_code_settings['open_desc'] ?? '');
 $oauth_providers = class_exists('\AKSRT\Auth\OAuth') ? \AKSRT\Auth\OAuth::get_instance()->get_auth_providers_data() : [];
 $wechat_qr = false;
 foreach ($oauth_providers as $provider) {
@@ -94,6 +97,7 @@ $oauth_bind_pass = $oauth_intent === 'bind'
 			<div class="floating-input has-action"><input type="password" name="password" id="<?php echo esc_attr($unique); ?>-register-password" autocomplete="new-password" minlength="6" required><label for="<?php echo esc_attr($unique); ?>-register-password"><?php esc_html_e('密码', 'aksrt'); ?></label><button type="button" class="password-show" data-password-show aria-label="<?php esc_attr_e('显示密码', 'aksrt'); ?>" aria-pressed="false"><i class="fa fas fa-eye"></i></button></div>
 			<?php if (!$omit_confirm) : ?><div class="floating-input has-action"><input type="password" name="password_confirm" id="<?php echo esc_attr($unique); ?>-register-confirm" autocomplete="new-password" minlength="6" required><label for="<?php echo esc_attr($unique); ?>-register-confirm"><?php esc_html_e('重复密码', 'aksrt'); ?></label><button type="button" class="password-show" data-password-show aria-label="<?php esc_attr_e('显示密码', 'aksrt'); ?>" aria-pressed="false"><i class="fa fas fa-eye"></i></button></div><?php endif; ?>
 			<?php if ($ref_mode !== 'hidden') : ?><div class="floating-input"><input name="ref" value="<?php echo esc_attr($ref_value); ?>" id="<?php echo esc_attr($unique); ?>-register-ref" <?php echo $ref_mode === 'required' ? 'required' : ''; ?>><label for="<?php echo esc_attr($unique); ?>-register-ref"><?php echo $ref_mode === 'required' ? esc_html__('推广码', 'aksrt') : esc_html__('推广码（选填）', 'aksrt'); ?></label></div><?php if ($ref_hint !== '') : ?><div class="sign-hint"><?php echo wp_kses_post($ref_hint); ?></div><?php endif; ?><?php endif; ?>
+			<?php if ($invite_mode !== 'hidden') : ?><div class="floating-input"><input name="invite_code" id="<?php echo esc_attr($unique); ?>-register-invite" data-invite-verify <?php echo $invite_mode === 'required' ? 'required' : ''; ?>><label for="<?php echo esc_attr($unique); ?>-register-invite"><?php echo $invite_mode === 'required' ? esc_html__('邀请码', 'aksrt') : esc_html__('邀请码（选填）', 'aksrt'); ?></label></div><small class="sign-hint" data-invite-feedback role="status" aria-live="polite" hidden></small><?php if ($invite_hint !== '') : ?><div class="sign-hint"><?php echo wp_kses_post($invite_hint); ?></div><?php endif; ?><?php endif; ?>
 			<?php if (!empty($agreement['enabled']) && !empty($agreement['required'])) : ?><label class="sign-agreement"><input type="checkbox" name="agree_terms" value="1" required><span><?php echo $agreement['label_html']; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped ?></span></label><?php elseif (!empty($agreement['enabled'])) : ?><div class="sign-agreement sign-agreement-implicit"><?php esc_html_e('注册即表示', 'aksrt'); ?><?php echo $agreement['label_html']; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped ?></div><?php endif; ?>
 			<?php if (function_exists('aksrt_render_captcha')) { aksrt_render_captcha('register'); } ?>
 			<input type="hidden" name="channel" value="<?php echo esc_attr($signup_type === 'phone' ? 'phone' : ''); ?>">