feat: live update log in UI and suppress lifecycle Telegram during SAC update

Poll remote update_script.log while SSH update runs; skip lifecycle notify
when host agent_update_state is running (SAC v0.5.1).

backend/app/services/ssh_connect.py

@@ -9,6 +9,7 @@ from dataclasses import dataclass
 from app.config import get_settings
 from app.models import Host
 
+SSH_MONITOR_UPDATE_LOG_PATH = "/var/log/update_script.log"
 SSH_MONITOR_UPDATE_SCRIPT = "/opt/scripts/update_ssh_monitor.sh"
 SSH_MONITOR_UPDATE_DIR = "/opt/scripts/update"
 SSH_MONITOR_REPO_NAME = "ssh-monitor"
@@ -549,3 +550,29 @@ def run_ssh_monitor_update(
             exit_code=updated.exit_code,
         )
     return updated
+
+
+def tail_ssh_monitor_update_log(
+    *,
+    target: str,
+    user: str,
+    password: str,
+    lines: int = 120,
+) -> str:
+    """Хвост /var/log/update_script.log на удалённом хосте (для live-лога в SAC UI)."""
+    safe_lines = max(20, min(int(lines), 400))
+    remote_cmd = (
+        f"test -r {SSH_MONITOR_UPDATE_LOG_PATH} && "
+        f"tail -n {safe_lines} {SSH_MONITOR_UPDATE_LOG_PATH} 2>/dev/null || true"
+    )
+    result = run_ssh_command(
+        target=target,
+        user=user,
+        password=password,
+        remote_cmd=remote_cmd,
+        command_timeout_sec=25,
+        need_root=True,
+        login_shell=False,
+    )
+    text = (result.stdout or "").strip()
+    return _truncate_output(text)