新增：聊天室留言板模态弹窗（仿商店样式）

点击工具栏「留言」按钮弹出留言板弹窗，不再跳转新页面。

新建文件：
- guestbook-modal.blade.php — 蓝白渐变标题栏、三Tab切换、留言卡片列表、内嵌写留言表单
- guestbook.js — 完整的AJAX加载/提交/删除逻辑，绑定所有事件

修改文件：
- toolbar.blade.php — 留言按钮 data-toolbar-url → data-toolbar-action
- toolbar.js — 添加 guestbook 动作
- chat-room.js — 静态导入 guestbook 模块
- frame.blade.php — 引入留言弹窗
- routes/web.php — 新增 guestbook.data JSON 路由
- GuestbookController.php — 新增 data() 方法

app/Http/Controllers/GuestbookController.php

@@ -15,6 +15,7 @@ use App\Http\Requests\StoreGuestbookRequest;
 use App\Models\Guestbook;
 use App\Models\User;
 use App\Services\MessageFilterService;
+use Illuminate\Http\JsonResponse;
 use Illuminate\Http\RedirectResponse;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Auth;
@@ -128,4 +129,69 @@ class GuestbookController extends Controller
 
         return back()->with('success', '该行留言已被抹除。');
     }
+
+    /**
+     * 返回留言列表 JSON（供聊天室模态弹窗 AJAX 使用）
+     */
+    public function data(Request $request): JsonResponse
+    {
+        $tab = $request->input('tab', 'public');
+        $page = (int) $request->input('page', 1);
+        $user = Auth::user();
+
+        $query = Guestbook::query()->orderByDesc('id');
+
+        if ($tab === 'inbox') {
+            $query->where('towho', $user->username);
+        } elseif ($tab === 'outbox') {
+            $query->where('who', $user->username);
+        } else {
+            $query->where(function ($q) use ($user) {
+                $q->where('secret', 0)
+                    ->orWhere('who', $user->username)
+                    ->orWhere('towho', $user->username);
+            });
+        }
+
+        $perPage = 15;
+        $total = $query->count();
+        $messages = $query->skip(($page - 1) * $perPage)->take($perPage)->get();
+
+        $items = $messages->map(function ($msg) use ($user) {
+            $isSecret = (bool) $msg->secret;
+            $isToMe = $msg->towho === $user->username;
+            $isFromMe = $msg->who === $user->username;
+            $canDelete = $isFromMe || $isToMe || $user->user_level >= 15;
+
+            return [
+                'id' => $msg->id,
+                'who' => $msg->who,
+                'towho' => $msg->towho ?: '',
+                'secret' => $isSecret,
+                'text_body' => $msg->text_body,
+                'post_time' => $msg->post_time?->diffForHumans() ?? '',
+                'timestamp' => $msg->post_time?->toIso8601String() ?? '',
+                'is_to_me' => $isToMe,
+                'is_from_me' => $isFromMe,
+                'can_delete' => $canDelete,
+                'who_avatar' => mb_substr($msg->who, 0, 1),
+            ];
+        });
+
+        // 获取所有用户名列表（供发信选择器使用）
+        $users = User::where('username', '!=', $user->username)
+            ->orderBy('username')
+            ->pluck('username');
+
+        return response()->json([
+            'ok' => true,
+            'items' => $items,
+            'total' => $total,
+            'page' => $page,
+            'per_page' => $perPage,
+            'has_more' => ($page * $perPage) < $total,
+            'users' => $users,
+            'tab' => $tab,
+        ]);
+    }
 }