fix: 修复页面间状态丢失问题并优化选择页面

- 修复选择审批人后再选择抄送人导致状态丢失的问题
- 使用独立的 sessionStorage key (selectedApprovers, selectedCc)
- 组件每次挂载时从 sessionStorage 恢复状态
- 只在提交/保存成功后清除 sessionStorage
- 优化人员选择页面布局和样式
- 更新 CLAUDE.md 文档记录问题和解决方案

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/Util/JwtUtil.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace App\Util;
+
+use Firebase\JWT\JWT;
+use Firebase\JWT\Key;
+use Exception;
+
+class JwtUtil
+{
+    private static string $secret = 'your-secret-key-change-in-production';
+    private static int $expire = 86400 * 7; // 7 days
+
+    /**
+     * 生成 Token
+     */
+    public static function encode(array $data): string
+    {
+        $payload = array_merge($data, [
+            'iat' => time(),
+            'exp' => time() + self::$expire,
+        ]);
+
+        return JWT::encode($payload, self::$secret, 'HS256');
+    }
+
+    /**
+     * 解析 Token
+     */
+    public static function decode(string $token): ?array
+    {
+        try {
+            $decoded = JWT::decode($token, new Key(self::$secret, 'HS256'));
+            return (array) $decoded;
+        } catch (Exception $e) {
+            return null;
+        }
+    }
+
+    /**
+     * 验证 Token
+     */
+    public static function verify(string $token): bool
+    {
+        return self::decode($token) !== null;
+    }
+}