fix: 修复审批详情显示实际审批人和飞书消息emoji编码

1. 审批详情显示修复
   - 新增 ApprovalService::getDetail() 方法
   - 从 form_data 获取用户实际选择的审批人和抄送人
   - 返回每个节点的 actual_approvers 和 approver_statuses
   - 修复详情页显示默认审批人而非实际审批人的问题

2. 飞书消息emoji编码修复
   - 修复 content 字段格式：应为 card 对象JSON字符串，不是 {"card":{...}}
   - 使用 JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES
   - 新增 HttpClient::httpPostJson() 方法处理预编码字段
   - 修复消息发送错误码 200621

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

backend/app/service/FeishuNotificationService.php

@@ -566,13 +566,19 @@ class FeishuNotificationService
             error_log('📤 发送飞书消息: app_id=' . $app['app_id'] . ', feishu_user_id=' . $feishuUserId);
             error_log('📦 消息卡片: ' . json_encode($card, JSON_UNESCAPED_UNICODE));
 
-            $response = HttpClient::httpPost(
+            // content 必须是 card 对象的 JSON 字符串，不是 {"card":{...}}
+            // JSON_UNESCAPED_UNICODE 保留 emoji
+            // JSON_UNESCAPED_SLASHES 避免 URL 中的 / 被转义为 \/
+            $contentJson = json_encode($card, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
+
+            $response = HttpClient::httpPostJson(
                 "https://open.feishu.cn/open-apis/im/v1/messages?receive_id_type=user_id",
                 [
                     'receive_id' => $feishuUserId,
                     'msg_type' => 'interactive',
-                    'content' => ['card' => $card],  // 直接传递数组，让 HttpClient 进行编码
+                    'content' => $contentJson,
                 ],
+                ['content'],  // content 字段是预编码的 JSON 字符串
                 [
                     'Authorization: Bearer ' . $token,
                 ]
@@ -707,13 +713,18 @@ class FeishuNotificationService
                         'operator' => $operatorName,
                     ];
 
-                    $response = HttpClient::httpPost(
+                    // content 必须是 card 对象的 JSON 字符串，不是 {"card":{...}}
+                    // JSON_UNESCAPED_UNICODE 保留 emoji
+                    // JSON_UNESCAPED_SLASHES 避免 URL 中的 / 被转义为 \/
+                    $contentJson = json_encode($updatedCard, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
+
+                    $response = HttpClient::httpPostJson(
                         "https://open.feishu.cn/open-apis/im/v1/messages/{$message->message_id}/update",
                         [
                             'msg_type' => 'interactive',
-                            // 直接传递数组，让 HttpClient 进行编码
-                            'content' => ['card' => $updatedCard],
+                            'content' => $contentJson,
                         ],
+                        ['content'],  // content 字段是预编码的 JSON 字符串
                         [
                             'Authorization: Bearer ' . $token,
                         ]
@@ -826,15 +837,18 @@ class FeishuNotificationService
 
             $apiUrl = "https://open.feishu.cn/open-apis/im/v1/messages?receive_id_type=user_id";
 
+            // content 必须是 JSON 字符串，使用 httpPostJson 避免二次编码
+            $contentJson = json_encode(['text' => $text], JSON_UNESCAPED_UNICODE);
+
             $requestData = [
                 'receive_id' => $feishuUserId,
                 'msg_type' => 'text',
-                'content' => json_encode(['text' => $text]),
+                'content' => $contentJson,
             ];
 
             error_log('📤 发送文本消息: feishu_user_id=' . $feishuUserId . ', text=' . substr($text, 0, 100));
 
-            $responseData = \app\util\HttpClient::httpPost($apiUrl, $requestData, [
+            $responseData = \app\util\HttpClient::httpPostJson($apiUrl, $requestData, ['content'], [
                 'Authorization: Bearer ' . $accessToken,
             ]);