fix: active anomalies not disappear after resolve

backend/main.py

@@ -229,7 +229,8 @@ async def get_system_metrics(limit: int = 60) -> list[dict]:
 
 @app.get("/api/active-anomalies", summary="Currently anomalous processes")
 async def get_active_anomalies() -> list[dict]:
-    """Latest snapshot per PID — only rows where is_anomaly=1."""
+    """Latest snapshot per PID — only rows where is_anomaly=1 and seen within last 30 s."""
+    cutoff = (datetime.now(timezone.utc) - timedelta(seconds=30)).isoformat()
     async with aiosqlite.connect(DB_PATH) as db:
         db.row_factory = aiosqlite.Row
         async with db.execute("""
@@ -239,9 +240,10 @@ async def get_active_anomalies() -> list[dict]:
                 SELECT pid, MAX(id) AS max_id FROM metrics GROUP BY pid
             ) latest ON m.id = latest.max_id
             WHERE m.is_anomaly = 1
+              AND m.timestamp >= ?
             ORDER BY m.cpu_percent DESC
             LIMIT 20
-        """) as cur:
+        """, (cutoff,)) as cur:
             return [dict(r) for r in await cur.fetchall()]