feat: game UID fully internal + remove multi-identity copy

- game_uid is now an internal param: auto-generated server-side
  (U + 12 hex) on register/bind-identity/install/admin-create/external
  register; player-supplied game_uid ignored
- Removed all player-facing UID inputs: register page, install page,
  identity bind modal, ticket-create 'your UID' field
- Removed player-facing UID display: identity table column,
  ticket detail/tracking reporter UID
- Removed '同一账号可绑定网易端 + 皮肤站身份' / '可绑定多个来源身份' copy
- Kept target_game_uid (reported player) and admin panel UID management
- settings-page skin-site placeholder updated

public/js/pages/home.js

@@ -65,7 +65,7 @@ const HomePage = {
     API.get(`/tickets/tracking?token=${token}`).then(tickets => {
       const t = tickets.find(x=>x.id===id);
       if(!t) return;
-      document.getElementById('tkd').innerHTML = `<div class="detail-section"><h4>基本信息</h4><div class="detail-row"><span class="lbl">标题</span><span class="val fb">${U.esc(t.title)}</span></div><div class="detail-row"><span class="lbl">类型</span><span class="val">${U.badge(t.type,'type')}</span></div><div class="detail-row"><span class="lbl">状态</span><span class="val">${U.badge(t.status,'status')}</span></div><div class="detail-row"><span class="lbl">提交者</span><span class="val">${U.esc(t.reporter_game_name)} (UID: ${U.esc(t.reporter_game_uid)})</span></div>${t.description?`<div class="detail-row"><span class="lbl">详情</span><span class="val">${U.esc(t.description)}</span></div>`:''}</div>
+      document.getElementById('tkd').innerHTML = `<div class="detail-section"><h4>基本信息</h4><div class="detail-row"><span class="lbl">标题</span><span class="val fb">${U.esc(t.title)}</span></div><div class="detail-row"><span class="lbl">类型</span><span class="val">${U.badge(t.type,'type')}</span></div><div class="detail-row"><span class="lbl">状态</span><span class="val">${U.badge(t.status,'status')}</span></div><div class="detail-row"><span class="lbl">提交者</span><span class="val">${U.esc(t.reporter_game_name)}</span></div>${t.description?`<div class="detail-row"><span class="lbl">详情</span><span class="val">${U.esc(t.description)}</span></div>`:''}</div>
         <form id="anon-reply-form" class="mt-4"><div class="form-group"><textarea id="anon-reply-content" rows="3" placeholder="追加补充信息..."></textarea></div><button type="submit" class="btn btn-p btn-sm"><i class="fas fa-reply"></i> 补充</button></form>`;
       document.getElementById('anon-reply-form').onsubmit = async e => {
         e.preventDefault();