fix: 批量改进 (#2/#23/#38/#39/#40/#47)

- Web: 隐藏 ICP 备案号（条件渲染），联系入口改为微信咨询（条件渲染，配置 wechat 字段后生效）
- backend: 拼音回填抽取为独立 cmd/backfill-pinyin 工具，不再在启动时运行
- backend: DB 连接池参数（max_idle_conns/max_open_conns）改为配置可控，默认 10/100
- backend: Inventory 反范式字段添加注释说明快照语义
- backend: 全量 handler 采用 util.RespondSuccess/RespondCreated 统一响应格式（51 处）

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/index.njk

@@ -555,7 +555,7 @@ details[open] .faq-q .icon { transform: rotate(45deg); }
           <li class="d-flex items-start gap-8 fs-sm text-gray-7"><i data-lucide="check" class="icon-sm text-brand flex-shrink-0 mt-2"></i>单门店 · 最多 3 用户</li>
           <li class="d-flex items-start gap-8 fs-sm text-gray-7"><i data-lucide="check" class="icon-sm text-brand flex-shrink-0 mt-2"></i>全部模块开放</li>
           <li class="d-flex items-start gap-8 fs-sm text-gray-7"><i data-lucide="check" class="icon-sm text-brand flex-shrink-0 mt-2"></i>Web 端 + 移动端</li>
-          <li class="d-flex items-start gap-8 fs-sm text-gray-7"><i data-lucide="check" class="icon-sm text-brand flex-shrink-0 mt-2"></i>邮件技术支持</li>
+          <li class="d-flex items-start gap-8 fs-sm text-gray-7"><i data-lucide="check" class="icon-sm text-brand flex-shrink-0 mt-2"></i>微信技术支持</li>
         </ul>
         <a href="/register/" class="btn btn-secondary w-full justify-center mt-auto">免费开通</a>
       </div>
@@ -585,7 +585,7 @@ details[open] .faq-q .icon { transform: rotate(45deg); }
           <li class="d-flex items-start gap-8 fs-sm text-gray-7"><i data-lucide="check" class="icon-sm text-brand flex-shrink-0 mt-2"></i>专属实施与培训服务</li>
           <li class="d-flex items-start gap-8 fs-sm text-gray-7"><i data-lucide="check" class="icon-sm text-brand flex-shrink-0 mt-2"></i>7×24 专属客户经理</li>
         </ul>
-        <a href="mailto:{{ site.support.email }}" class="btn btn-secondary w-full justify-center mt-auto">联系销售</a>
+        {% if site.support.wechat %}<a href="#" class="btn btn-secondary w-full justify-center mt-auto">微信咨询：{{ site.support.wechat }}</a>{% else %}<a href="mailto:{{ site.support.email }}" class="btn btn-secondary w-full justify-center mt-auto">联系销售</a>{% endif %}
       </div>
     </div>
   </div>
@@ -639,7 +639,7 @@ details[open] .faq-q .icon { transform: rotate(45deg); }
       </div>
       <div class="d-flex flex-col gap-12 items-start">
         <a href="/register/" class="btn btn-primary btn-lg">立即开通试用<i data-lucide="arrow-right" class="icon"></i></a>
-        <a href="mailto:{{ site.support.email }}?subject=咨询岩美连锁版" class="btn btn-secondary btn-lg"><i data-lucide="mail" class="icon"></i>邮件咨询</a>
+        {% if site.support.wechat %}<a href="#" class="btn btn-secondary btn-lg"><i data-lucide="message-circle" class="icon"></i>微信咨询：{{ site.support.wechat }}</a>{% else %}<a href="mailto:{{ site.support.email }}?subject=咨询岩美连锁版" class="btn btn-secondary btn-lg"><i data-lucide="mail" class="icon"></i>邮件咨询</a>{% endif %}
       </div>
     </div>
   </div>