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/operation_log.json

@@ -1,75 +1,90 @@
 {
     "0": {
-        "timestamp": "2025-12-12 04:47:50",
+        "timestamp": "2025-12-12 08:46:41",
         "action": "管理员登录",
         "ip": "::1"
     },
     "1": {
-        "timestamp": "2025-12-12 04:17:07",
+        "timestamp": "2025-12-12 08:05:44",
         "action": "管理员登录",
         "ip": "::1"
     },
     "2": {
+        "timestamp": "2025-12-12 08:00:34",
+        "action": "管理员登录",
+        "ip": "::1"
+    },
+    "3": {
+        "timestamp": "2025-12-12 04:47:50",
+        "action": "管理员登录",
+        "ip": "::1"
+    },
+    "4": {
+        "timestamp": "2025-12-12 04:17:07",
+        "action": "管理员登录",
+        "ip": "::1"
+    },
+    "5": {
         "timestamp": "2025-11-11 13:41:58",
         "action": "管理员登录",
         "ip": "113.87.139.184"
     },
-    "3": {
+    "6": {
         "timestamp": "2025-11-06 08:31:27",
         "action": "管理员登录",
         "ip": "113.87.138.191"
     },
-    "4": {
+    "7": {
         "timestamp": "2025-11-05 14:45:57",
         "action": "管理员登录",
         "ip": "113.87.138.191"
     },
-    "5": {
+    "8": {
         "timestamp": "2025-11-05 14:34:30",
         "action": "管理员登录",
         "ip": "113.87.138.191"
     },
-    "6": {
+    "9": {
         "timestamp": "2025-11-05 09:47:16",
         "action": "管理员登录",
         "ip": "113.87.138.191"
     },
-    "7": {
+    "10": {
         "timestamp": "2025-11-01 23:18:46",
         "action": "管理员登录",
         "ip": "113.87.139.206"
     },
-    "8": {
+    "11": {
         "timestamp": "2025-10-31 23:11:13",
         "action": "管理员登录",
         "ip": "113.84.8.124"
     },
-    "9": {
+    "12": {
         "timestamp": "2025-10-31 10:20:41",
         "action": "管理员注销",
         "ip": "113.87.137.255"
     },
-    "10": {
+    "13": {
         "timestamp": "2025-10-31 10:18:31",
         "action": "管理员登录",
         "ip": "113.87.137.255"
     },
-    "11": {
+    "14": {
         "timestamp": "2025-10-31 09:08:47",
         "action": "管理员登录",
         "ip": "113.87.137.255"
     },
-    "12": {
+    "15": {
         "timestamp": "2025-10-30 21:05:23",
         "action": "管理员登录",
         "ip": "113.87.139.170"
     },
-    "13": {
+    "16": {
         "timestamp": "2025-10-30 17:28:24",
         "action": "管理员注销",
         "ip": "113.87.137.255"
     },
-    "14": {
+    "17": {
         "timestamp": "2025-10-30 17:14:21",
         "action": "管理员登录",
         "ip": "113.87.137.255"