feat: 水印移到全局Shell，资产和里程页面都有水印

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/Shell.tsx

@@ -1,4 +1,5 @@
-import { useState, useEffect, type ComponentType } from 'react';
+import { useState, useEffect, useMemo, type ComponentType } from 'react';
+import { useAuth } from '../auth/useAuth';
 
 export interface ModuleConfig {
   id: string;
@@ -55,8 +56,22 @@ export function Shell({ modules }: { modules: ModuleConfig[] }) {
 
   const ActiveComponent = modules.find((m) => m.id === activeModule)?.component ?? modules[0]?.component;
 
+  const { user } = useAuth();
+  const watermarkText = useMemo(() => {
+    const name = user?.userName || '未登录';
+    const time = new Date().toLocaleString('zh-CN', { year: 'numeric', month: '2-digit', day: '2-digit', hour: '2-digit', minute: '2-digit', second: '2-digit', hour12: false }).replace(/\//g, '-');
+    return `${name}-${time}`;
+  }, [user]);
+
   return (
     <div className="flex min-h-screen">
+      {/* 全局水印 */}
+      <div className="fixed inset-0 pointer-events-none z-[9999] overflow-hidden" style={{ opacity: 0.06 }}>
+        <div className="absolute inset-0" style={{
+          backgroundImage: `url("data:image/svg+xml,${encodeURIComponent(`<svg xmlns='http://www.w3.org/2000/svg' width='320' height='200'><text x='50%' y='50%' text-anchor='middle' dominant-baseline='middle' font-size='14' font-family='sans-serif' fill='%23000' transform='rotate(-25 160 100)'>${watermarkText}</text></svg>`)}")`,
+          backgroundRepeat: 'repeat',
+        }} />
+      </div>
       {/* Web 侧边栏 (md 及以上) */}
       <nav className="hidden md:flex flex-col items-center w-16 bg-white border-r border-gray-100 fixed top-0 left-0 h-full z-50 py-6 gap-2">
         {modules.map((m) => {