feat: add top navbar to /share page, move nav links out of upload zone

- Add NavBar component with app branding and conditional nav links
- NavBar shows "个人中心" for token_manage permission, "管理控制台" for user_manage
- Restructure share.tsx with flex column layout (NavBar + 3-column grid)
- Clean up panel-left.tsx: remove auth check, nav links, and unused styles

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frontend/src/page/share/component/nav-bar.tsx

@@ -0,0 +1,81 @@
+import React, {useEffect, useState} from 'react';
+import {createUseStyles} from 'react-jss';
+
+const useStyle = createUseStyles({
+    nav: {
+        display: 'flex',
+        alignItems: 'center',
+        justifyContent: 'space-between',
+        padding: '0 24px',
+        height: '48px',
+        backgroundColor: '#2c9678',
+        boxShadow: '0 2px 6px rgba(0,0,0,0.15)',
+        flexShrink: 0,
+    },
+    brand: {
+        color: 'white',
+        fontWeight: 700,
+        fontSize: '18px',
+        letterSpacing: '1px',
+        textDecoration: 'none',
+    },
+    links: {
+        display: 'flex',
+        gap: '8px',
+        alignItems: 'center',
+    },
+    link: {
+        color: 'rgba(255,255,255,0.9)',
+        fontSize: '13px',
+        textDecoration: 'none',
+        padding: '5px 12px',
+        borderRadius: '4px',
+        transition: 'background-color 0.2s',
+        '&:hover': {
+            backgroundColor: 'rgba(255,255,255,0.2)',
+            color: 'white',
+        },
+    },
+    divider: {
+        color: 'rgba(255,255,255,0.4)',
+        fontSize: '13px',
+    },
+});
+
+export const NavBar: React.FC = () => {
+    const style = useStyle();
+    const [isAdmin, setIsAdmin] = useState(false);
+    const [hasTokenPerm, setHasTokenPerm] = useState(false);
+
+    useEffect(() => {
+        fetch('/api/uauth/me').then(async res => {
+            if (res.ok) {
+                const json = await res.json();
+                const perms: string[] = json.data?.permissions ?? [];
+                setIsAdmin(perms.includes('user_manage'));
+                setHasTokenPerm(perms.includes('token_manage'));
+            }
+        }).catch(() => {});
+    }, []);
+
+    const showLinks = isAdmin || hasTokenPerm;
+
+    return (
+        <nav className={style.nav}>
+            <a href="/share" className={style.brand}>UShare</a>
+            {showLinks && (
+                <div className={style.links}>
+                    {hasTokenPerm && (
+                        <a href="/self" className={style.link}>个人中心</a>
+                    )}
+                    {isAdmin && hasTokenPerm && (
+                        <span className={style.divider}>|</span>
+                    )}
+                    {isAdmin && (
+                        <a href="/admin" className={style.link}>管理控制台</a>
+                    )}
+                </div>
+            )}
+        </nav>
+    );
+};