feat(tickets): make ticket title/content/reply length limits configurable

Add ticket_title_max / ticket_content_max / ticket_reply_max to the
users/ticket schema (PHP + SPA) with clamped TicketSettings readers.
All write paths (front REST, admin REST, note REST, native admin page)
and front-end maxlength/counters now read the configured limits.
Remove the hardcoded TICKET_CONTENT_MAX constant.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Ticket/TicketRestAdmin.php

@@ -311,10 +311,10 @@ final class TicketRestAdmin {
         if ($user_id <= 0 || !get_userdata($user_id)) {
             return new \WP_Error('aksrt_ticket_user', __('请选择工单所属用户', 'aksrt'), ['status' => 400]);
         }
-        if ($title === '' || mb_strlen($title) > 200) {
+        if ($title === '' || mb_strlen($title) > TicketSettings::title_max()) {
             return new \WP_Error('aksrt_ticket_title', __('请填写有效的工单标题', 'aksrt'), ['status' => 400]);
         }
-        if ($content === '' || mb_strlen($content) > 5000) {
+        if ($content === '' || mb_strlen($content) > TicketSettings::content_max()) {
             return new \WP_Error('aksrt_ticket_content', __('请填写有效的问题描述', 'aksrt'), ['status' => 400]);
         }
         if (!TicketTypeService::exists($type_id)) {
@@ -356,7 +356,7 @@ final class TicketRestAdmin {
             return new \WP_Error('aksrt_ticket_closed', __('工单已关闭，无法回复', 'aksrt'), ['status' => 409]);
         }
         $content = trim((string) $request->get_param('content'));
-        if ($content === '' || mb_strlen($content) > 3000) {
+        if ($content === '' || mb_strlen($content) > TicketSettings::reply_max()) {
             return new \WP_Error('aksrt_ticket_reply_content', __('请填写有效的回复内容', 'aksrt'), ['status' => 400]);
         }
         $quote_id = absint($request->get_param('quote_reply_id'));