Add systemd timer fallback when crontab unavailable

- Try crontab first, fall back to systemd timer
- If neither available, still deploy script but warn user
- Update frontend to show scheduling method (cron/systemd/none)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/monitors.py

@@ -298,22 +298,61 @@ class MonitorService:
                     "error": f"Failed to make script executable: {error_detail}",
                 }
 
-            # Add cronjob entry (remove existing entry first to avoid duplicates)
+            # Try to add cronjob entry (crontab may not be available on all systems)
             cron_cmd = f"(crontab -l 2>/dev/null | grep -v '{script_filename}'; echo '{cronjob_entry}') | crontab -"
             cron_result = ssh.execute(hostname, cron_cmd, username, port)
-            if not cron_result.success:
-                return {
-                    "status": "failed",
-                    "error": f"Failed to add cronjob: {cron_result.stderr}",
-                }
+
+            scheduling_method = None
+            scheduling_info = None
+
+            if cron_result.success:
+                scheduling_method = "crontab"
+                scheduling_info = cronjob_entry
+            else:
+                # Try systemd timer as fallback
+                timer_name = f"kuma-push-{push_metric}-{monitor_id}"
+                timer_content = f"""[Unit]
+Description=Kuma Push Monitor - {push_metric}
+
+[Timer]
+OnBootSec=1min
+OnUnitActiveSec={interval_minutes}min
+AccuracySec=1s
+
+[Install]
+WantedBy=timers.target
+"""
+                service_content = f"""[Unit]
+Description=Kuma Push Monitor - {push_metric}
+
+[Service]
+Type=oneshot
+ExecStart={script_path}
+"""
+                # Write timer and service files
+                timer_path = f"/etc/systemd/system/{timer_name}.timer"
+                service_path = f"/etc/systemd/system/{timer_name}.service"
+
+                timer_cmd = f"sudo tee {timer_path} > /dev/null << 'KUMA_TIMER_EOF'\n{timer_content}KUMA_TIMER_EOF"
+                service_cmd = f"sudo tee {service_path} > /dev/null << 'KUMA_SERVICE_EOF'\n{service_content}KUMA_SERVICE_EOF"
+
+                timer_result = ssh.execute(hostname, timer_cmd, username, port)
+                if timer_result.success:
+                    service_result = ssh.execute(hostname, service_cmd, username, port)
+                    if service_result.success:
+                        # Enable and start the timer
+                        enable_cmd = f"sudo systemctl daemon-reload && sudo systemctl enable --now {timer_name}.timer"
+                        enable_result = ssh.execute(hostname, enable_cmd, username, port)
+                        if enable_result.success:
+                            scheduling_method = "systemd"
+                            scheduling_info = f"{timer_name}.timer"
 
             # Run the script once immediately to verify it works
             run_result = ssh.execute(hostname, script_path, username, port, timeout=30)
 
-            return {
+            result = {
                 "status": "deployed",
                 "script_path": script_path,
-                "cronjob": cronjob_entry,
                 "initial_run": {
                     "success": run_result.success,
                     "stdout": run_result.stdout,
@@ -321,6 +360,19 @@ class MonitorService:
                 },
             }
 
+            if scheduling_method:
+                result["scheduling"] = {
+                    "method": scheduling_method,
+                    "info": scheduling_info,
+                }
+            else:
+                result["scheduling"] = {
+                    "method": "none",
+                    "warning": "Neither crontab nor systemd available. Script deployed but not scheduled.",
+                }
+
+            return result
+
         except Exception as e:
             logger.exception(f"Failed to deploy push script to {hostname}")
             return {