feat: 修改助手名字，删除黑暗模式按钮

src/components/chat/WelcomeScreen.vue

@@ -2,7 +2,7 @@
   <div class="welcome-screen">
     <!-- Logo 和标题 -->
     <div class="welcome-header">
-      <h1 class="title">教研聊天助手</h1>
+      <h1 class="title">学习、教学、科研聊天助手</h1>
     </div>
 
     <!-- 功能卡片 -->

src/components/sidebar/ChatSidebar.vue

@@ -124,21 +124,21 @@
       </div>
 
       <!-- 底部操作 -->
-      <div class="sidebar-footer">
+      <!-- <div class="sidebar-footer">
         <button class="footer-btn" @click="toggleTheme" title="切换主题">
           <Sun v-if="currentTheme === 'light'" :size="18" />
           <Moon v-else-if="currentTheme === 'dark'" :size="18" />
           <Monitor v-else :size="18" />
         </button>
-        <!-- 键盘快捷键 -->
-        <!-- <button class="footer-btn" @click="openShortcuts" title="快捷键">
+        键盘快捷键
+        <button class="footer-btn" @click="openShortcuts" title="快捷键">
           <Keyboard :size="18" />
-        </button> -->
-        <!-- dev人员可用 -->
-        <!-- <button class="footer-btn" @click="openSettings" title="设置">
+        </button>
+        dev人员可用
+        <button class="footer-btn" @click="openSettings" title="设置">
           <Settings :size="18" />
-        </button> -->
-      </div>
+        </button>
+      </div> -->
     </div>
 
     <!-- 拖拽调整宽度 -->
@@ -157,9 +157,6 @@ import {
   Plus,
   Pin,
   MessageSquare,
-  Sun,
-  Moon,
-  Monitor,
   Sparkles,
   ChevronDown,
   Check,
@@ -688,7 +685,5 @@ if (typeof window !== "undefined") {
   height: 100%;
   cursor: col-resize;
   z-index: 10;
-
-
 }
 </style>