feat: 添加基金邮件定时发送功能并优化邮件内容格式

- 新增宝塔面板定时任务脚本 cron_send_email.php
- 添加手动发送邮件按钮到管理界面
- 使用PHPMailer替代原始SMTP实现
- 优化邮件内容格式，按涨跌幅排序基金数据
- 增加邮件发送时间窗口判断逻辑
- 更新项目文档说明定时任务配置

data/fund_history.json

@@ -61,57 +61,57 @@
     "today_data": {
         "003766": {
             "date": "2025-12-12",
-            "change": 0.6,
+            "change": 0.97,
             "name": "广发创业板ETF发起式联接C"
         },
         "008327": {
             "date": "2025-12-12",
-            "change": 1.63,
+            "change": 1.38,
             "name": "东财通信C"
         },
         "012863": {
             "date": "2025-12-12",
-            "change": -0.63,
+            "change": 0.18,
             "name": "汇添富中证电池主题ETF发起式联接C"
         },
         "023350": {
             "date": "2025-12-12",
-            "change": 0.56,
+            "change": -0.29,
             "name": "诺安多策略混合C"
         },
         "017560": {
             "date": "2025-12-12",
-            "change": 0.48,
+            "change": 2.1,
             "name": "华安上证科创板芯片ETF发起式联接C"
         },
         "011815": {
             "date": "2025-12-12",
-            "change": 0.58,
+            "change": 0.69,
             "name": "恒越优势精选混合A"
         },
         "003598": {
             "date": "2025-12-12",
-            "change": 0.47,
+            "change": 0.61,
             "name": "华商润丰灵活配置混合A"
         },
         "004206": {
             "date": "2025-12-12",
-            "change": 0.5,
+            "change": 0.77,
             "name": "华商元亨混合A"
         },
         "022365": {
             "date": "2025-12-12",
-            "change": 1.14,
+            "change": 1.19,
             "name": "永赢科技智选混合发起C"
         },
         "022364": {
             "date": "2025-12-12",
-            "change": 1.14,
+            "change": 1.19,
             "name": "永赢科技智选混合发起A"
         },
         "011103": {
             "date": "2025-12-12",
-            "change": 1.08,
+            "change": 1.98,
             "name": "天弘中证光伏产业指数C"
         }
     },