feat: add user management system with roles and permissions

- Introduce SQLite persistence via GORM (stored at <data>/.ushare.db)
- Add Role model with two built-in roles: admin (all perms) and user (upload only)
- Add three permissions: user_manage, upload, token_manage (reserved)
- Rewrite UserManager: DB-backed login with in-memory session tokens
- Auto-seed default roles and admin user on first startup
- Add AuthPermission middleware for fine-grained permission checks
- Add /api/uauth/me endpoint for current session info
- Add /api/admin/* CRUD routes for user and role management
- Add admin console page (/admin) with user table and role permissions view
- Show admin console link in share page for users with user_manage permission

🤖 Generated with [Qoder][https://qoder.com]

frontend/src/page/share/component/panel-left.tsx

@@ -1,6 +1,6 @@
 import {createUseStyles} from "react-jss";
 import {UButton} from "../../../component/button/u-button.tsx";
-import React, {useState} from "react";
+import React, {useEffect, useState} from "react";
 import {useStore} from "../../../store/share.ts";
 import {message} from "../../../hook/message/u-message.tsx";
 import {useFileUpload} from "../../../api/upload.ts";
@@ -59,7 +59,17 @@ const useUploadStyle = createUseStyles({
         borderRadius: '50%',
         cursor: 'pointer',
         '&:hover': {}
-    }
+    },
+    adminLink: {
+        display: 'block',
+        textAlign: 'center',
+        marginTop: '16px',
+        color: '#2c9678',
+        fontSize: '12px',
+        textDecoration: 'none',
+        opacity: 0.8,
+        '&:hover': {opacity: 1, textDecoration: 'underline'},
+    },
 })
 
 const useShowStyle = createUseStyles({
@@ -179,6 +189,17 @@ const PanelLeftUpload: React.FC<{ set_code: (code:string) => void }> = ({set_cod
     const style = useUploadStyle()
     const {file, setFile} = useStore()
     const {uploadFile, progress, loading} = useFileUpload();
+    const [isAdmin, setIsAdmin] = 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'));
+            }
+        }).catch(() => {});
+    }, []);
 
     function onFileSelect() {
         // @ts-ignore
@@ -225,6 +246,9 @@ const PanelLeftUpload: React.FC<{ set_code: (code:string) => void }> = ({set_cod
                     <div className={style.name}>{file.name}</div>
                 </div>
             }
+            {isAdmin && (
+                <a href="/admin" className={style.adminLink}>管理控制台</a>
+            )}
         </div>
     </div>
 }