fix: prevent duplicate host_silence problems per host (0.4.8)

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/tests/test_host_silence_scan.py

@@ -82,6 +82,43 @@ def test_scan_does_not_duplicate_open_problem(db_session, scan_settings):
     assert len(problems) == 1
 
 
+def test_scan_does_not_duplicate_after_correlation_window(db_session, scan_settings, monkeypatch):
+    """host_silence — одна open-проблема на хост, даже если прошло > correlation window."""
+    monkeypatch.setenv("SAC_PROBLEM_CORRELATION_WINDOW_MINUTES", "60")
+    get_settings.cache_clear()
+
+    hb = _ingest(
+        db_session,
+        type="agent.heartbeat",
+        category="agent",
+        severity="info",
+        title="hb",
+        summary="heartbeat",
+    )
+    hb.received_at = datetime.now(timezone.utc) - timedelta(hours=2)
+    db_session.flush()
+
+    t0 = datetime.now(timezone.utc)
+    first = run_host_silence_scan(db_session, now=t0)
+    assert first[0].created is True
+    first[0].problem.last_seen_at = t0 - timedelta(hours=2)
+    db_session.flush()
+
+    later = run_host_silence_scan(db_session, now=t0 + timedelta(hours=3))
+    assert len(later) == 1
+    assert later[0].created is False
+    assert later[0].problem.id == first[0].problem.id
+
+    problems = db_session.scalars(
+        select(Problem).where(
+            Problem.host_id == hb.host_id,
+            Problem.rule_id == RULE_HOST_SILENCE,
+            Problem.status == "open",
+        )
+    ).all()
+    assert len(problems) == 1
+
+
 def test_scan_skips_host_without_heartbeat(db_session, scan_settings):
     _ingest(
         db_session,