Dashboard: show online machines and live trade feed with polling.

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

app/db.py

@@ -141,6 +141,39 @@ def list_machines(conn: sqlite3.Connection) -> list[dict]:
     return [row_to_dict(r) for r in cur.fetchall()]
 
 
+ONLINE_SECONDS = 180  # 与下载中心一致：3 分钟内心跳视为在线
+
+
+def list_machines_for_user(conn: sqlite3.Connection, user: dict) -> list[dict]:
+    if user.get("role") == "admin":
+        items = list_machines(conn)
+    else:
+        cur = conn.execute(
+            """
+            SELECT DISTINCT m.* FROM machines m
+            JOIN activations act ON act.machine_id = m.id
+            WHERE act.account_id=?
+            ORDER BY m.id DESC
+            """,
+            (user.get("account_id"),),
+        )
+        items = [row_to_dict(r) for r in cur.fetchall()]
+    return annotate_machines_online(items)
+
+
+def annotate_machines_online(machines: list[dict], now_ts: Optional[float] = None) -> list[dict]:
+    ts = now_ts if now_ts is not None else now()
+    for m in machines:
+        last = m.get("last_seen_at")
+        try:
+            online = bool(last and (ts - float(last)) <= ONLINE_SECONDS)
+        except (TypeError, ValueError):
+            online = False
+        m["online"] = online
+        m["online_label"] = "在线" if online else "离线"
+    return machines
+
+
 def create_activation(
     conn: sqlite3.Connection,
     account_id: int,