fix(theme): schooltheme 补 item 级 adminOnly（审计发现普通用户导航出现「本校默认」）

步骤 4 harness 取证（role=user dump）发现 NAV_THEME.schooltheme 漏标 adminOnly: true，
item 级过滤未生效（ADMIN_PANES 兜底仍在，直达 URL 落 noperm 黄条验证通过）。
修复后重验：user 导航无「本校默认」、有「我的主题」、直达 ?pane=schooltheme 落 noperm；主构建绿

src/views/Settings.vue

@@ -449,7 +449,7 @@ const NAV_ACCOUNT: NavItem[] = [
 ];
 const NAV_THEME: NavItem[] = [
     { key: "mytheme", name: "我的主题", icon: svgWrap('<circle cx="12" cy="12" r="9"/><path d="M12 3a9 9 0 0 0 0 18c1.5 0 2-1 2-2s-1-1.5-1-2.5 1-2 2.5-2H19a2 2 0 0 0 2-2 9 9 0 0 0-9-9z"/><circle cx="7.5" cy="11" r="1"/><circle cx="12" cy="7.5" r="1"/><circle cx="16.5" cy="11" r="1"/>') },
-    { key: "schooltheme", name: "本校默认", icon: svgWrap('<path d="M4 21V8l8-5 8 5v13"/><path d="M4 21h16"/><path d="M12 11v4"/><circle cx="12" cy="9" r="2"/>') },
+    { key: "schooltheme", name: "本校默认", icon: svgWrap('<path d="M4 21V8l8-5 8 5v13"/><path d="M4 21h16"/><path d="M12 11v4"/><circle cx="12" cy="9" r="2"/>'), adminOnly: true },
 ];
 const NAV_APPEARANCE: NavItem[] = [
     { key: "logo", name: "LOGO 设置", icon: svgWrap('<rect x="3" y="4" width="18" height="16" rx="2"/><circle cx="8.5" cy="9.5" r="1.5"/><path d="M21 15l-5-5L5 20"/>') },