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/ticket-create.js

@@ -35,7 +35,7 @@ const TicketCreate = {
         this.identities = list || [];
         const sel = container.querySelector('#identity-select');
         if (sel && this.identities.length > 1) {
-          sel.innerHTML = this.identities.map((it, i) => `<option value="${i}">${U.esc(it.source)} — ${U.esc(it.game_name)}${it.game_uid ? ' (UID: ' + U.esc(it.game_uid) + ')' : ''}</option>`).join('');
+          sel.innerHTML = this.identities.map((it, i) => `<option value="${i}">${U.esc(it.source)} — ${U.esc(it.game_name)}</option>`).join('');
           sel.closest('.form-group').classList.remove('hidden');
         }
       }).catch(() => {});
@@ -68,18 +68,11 @@ const TicketCreate = {
             ${user ? `<div class="form-group hidden" id="identity-group">
               <label>使用身份</label>
               <select id="identity-select"></select>
-              <span class="help">同一账号可绑定网易端 + 皮肤站身份</span>
             </div>` : ''}
 
-            <div class="grid-2">
-              <div class="form-group">
-                <label>您的游戏名称 *</label>
-                <input name="reporter_game_name" required placeholder="Minecraft ID" value="${U.esc(prefill?.game_name || user?.game_name || '')}" ${prefill?.game_name ? 'readonly' : ''}>
-              </div>
-              <div class="form-group">
-                <label>您的游戏UID (可选)</label>
-                <input name="reporter_game_uid" placeholder="游戏UID(选填)" value="${U.esc(prefill?.game_uid || user?.game_uid || '')}" ${prefill?.game_uid ? 'readonly' : ''}>
-              </div>
+            <div class="form-group">
+              <label>您的游戏名称 *</label>
+              <input name="reporter_game_name" required placeholder="Minecraft ID" value="${U.esc(prefill?.game_name || user?.game_name || '')}" ${prefill?.game_name ? 'readonly' : ''}>
             </div>
 
             ${isReport ? `