feat: add Uptime Kuma heartbeat monitoring

- Add heartbeat configuration to config.yaml
- Implement HeartbeatMonitor class in watch.py
- Send heartbeat every 40 seconds to Uptime Kuma push endpoint
- Update config.yaml.example with heartbeat settings
- Add heartbeat logging at INFO level

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

config.yaml.example

@@ -1,5 +1,27 @@
 # Excel to SQL Server Migration Configuration
 
+# ================= 定时检查参数 =================
+check_interval_minutes: 5   # 每隔多少分钟扫描一次源文件
+
+# ================= 日志配置 =================
+logging:
+  level: "INFO"              # DEBUG / INFO / WARNING
+  log_dir: "logs"            # 日志目录（相对于项目根目录）
+  max_keep_days: 7          # 日志文件保留天数
+
+# ================= Uptime Kuma 心跳检测 =================
+heartbeat:
+  enabled: false             # 是否启用心跳检测
+  interval_seconds: 40       # 心跳发送间隔（秒）
+  url: "YOUR_UPTIME_KUMA_PUSH_URL"  # Uptime Kuma 推送端点 URL
+
+# ================= LAN 源文件路径 =================
+# key = 本地相对路径 (对应 tables.sources[].file)
+# value = 局域网 UNC 绝对路径
+lan_sources:
+  "PG/生产执行卡2022.xlsm": "\\\\192.168.110.113\\生产执行卡\\往年生产执行卡\\生产执行卡2022.xlsm"
+  # ... 其他 LAN 源文件路径
+
 # ================= SQL Server 连接 =================
 sql_server:
   driver: "ODBC Driver 18 for SQL Server"