feat(posts): add @mention highlighting and vote segment display

- Parse post content to highlight @mentions with blue styling
- Render vote segments from post data with formatted options display
- Add MessageSegment interface and segments/is_vote fields to Post type
- Update API base URL and branding from Carrot BBS to WithYou

src/pages/Dashboard.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect } from 'react'
+import { useState, useEffect } from 'react'
 import { Users, FileText, MessageSquare, Clock, TrendingUp, Calendar, CalendarDays, CalendarRange } from 'lucide-react'
 import { StatsCard } from '@/components/StatsCard'
 import { ActivityChart } from '@/components/ActivityChart'
@@ -78,7 +78,7 @@ export default function Dashboard() {
     <div className="space-y-6">
       <div>
         <h1 className="text-3xl font-bold">Dashboard</h1>
-        <p className="text-muted-foreground">欢迎来到 Carrot BBS 管理后台</p>
+        <p className="text-muted-foreground">欢迎来到 WithYou 管理后台</p>
       </div>
       
       {/* 统计卡片 */}

src/pages/Login.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react'
+import { useState } from 'react'
 import { useNavigate, useLocation } from 'react-router-dom'
 import { useAuthStore } from '@/stores/authStore'
 import { Button } from '@/components/ui/button'
@@ -62,7 +62,7 @@ export default function Login() {
               <span className="text-2xl font-bold">C</span>
             </div>
           </div>
-          <CardTitle className="text-2xl font-bold">Carrot BBS</CardTitle>
+          <CardTitle className="text-2xl font-bold">WithYou</CardTitle>
           <CardDescription>管理后台登录</CardDescription>
         </CardHeader>
         <form onSubmit={handleSubmit}>

src/pages/Posts.tsx

@@ -636,8 +636,25 @@ export default function Posts() {
               <div className="space-y-4">
                 <h3 className="text-2xl font-bold text-slate-900 leading-tight">{selectedPost.title}</h3>
                 <div className="prose prose-slate max-w-none">
-                  <p className="text-slate-700 whitespace-pre-wrap leading-relaxed text-base">{selectedPost.content}</p>
+                  <p className="text-slate-700 whitespace-pre-wrap leading-relaxed text-base">
+                    {selectedPost.content?.split(/@(\S+)/g).map((part, i) =>
+                      i % 2 === 1 ? <span key={i} className="text-blue-600 font-medium">@{part}</span> : part
+                    )}
+                  </p>
                 </div>
+                {/* 投票信息（从 segments 解析） */}
+                {selectedPost.segments?.filter(s => s.type === 'vote').map((seg, i) => (
+                  <div key={i} className="mt-3 p-4 rounded-lg border border-slate-200 bg-slate-50">
+                    <div className="flex items-center gap-2 text-sm font-medium text-slate-700 mb-3">
+                      <span>📊 投票</span>
+                    </div>
+                    {seg.data?.options?.map((opt: any, j: number) => (
+                      <div key={j} className="py-1.5 text-slate-600">
+                        {j + 1}. {opt.content}
+                      </div>
+                    ))}
+                  </div>
+                ))}
               </div>
 
               {/* 图片展示 */}