修复桌面端界面显示与稳定性问题

frontend/src/components/DesktopLayout.vue

@@ -3,7 +3,10 @@
     <aside class="desktop-sidebar">
       <header class="sidebar-head">
         <div class="sidebar-title-row">
-          <h1>{{ TEXT.common.appName }}</h1>
+          <div class="sidebar-app-brand">
+            <img class="sidebar-app-icon" src="/icons/ctms-icon-192.png" alt="" aria-hidden="true" />
+            <h1>{{ TEXT.common.appName }}</h1>
+          </div>
 
           <button v-if="showSidebarProjectChooser" class="study-switcher-trigger empty" type="button" @click="openDesktopProjectEntry">
             选择项目
@@ -1383,6 +1386,23 @@ useDesktopShortcuts(
   white-space: nowrap;
 }
 
+.sidebar-app-brand {
+  display: inline-grid;
+  min-width: 0;
+  grid-template-columns: 30px minmax(0, 1fr);
+  align-items: center;
+  gap: 9px;
+}
+
+.sidebar-app-icon {
+  width: 30px;
+  height: 30px;
+  border-radius: 8px;
+  background: #ffffff;
+  box-shadow: 0 8px 18px rgba(15, 23, 42, 0.14);
+  object-fit: contain;
+}
+
 .icon-button {
   width: 32px;
   height: 32px;
@@ -2357,13 +2377,6 @@ useDesktopShortcuts(
 :global(.desktop-preferences-dialog .el-dialog__body) {
   padding: 0;
   background: transparent;
-  display: flex;
-  flex-direction: column;
-}
-
-:global(.desktop-preferences-dialog .el-dialog__body > *) {
-  flex: 1;
-  min-height: 0;
 }
 
 :global([data-ctms-theme="dark"] .desktop-workbench) {