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>

.gitignore

@@ -33,3 +33,6 @@ config.yaml
 # Excel temp files
 Excel/
 *.tmp
+
+.claude/
+.agents/