feat: add per-account daily open hard limit across all exchanges

Enforce optional DAILY_OPEN_HARD_LIMIT in precheck_risk and can_trade, keep AI alerts at DAILY_OPEN_ALERT_THRESHOLD, and document env setup for all four instances.

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

strategy_trend_register.py

@@ -1484,10 +1484,18 @@ def load_trend_page_context(conn, request_obj, cfg: dict) -> dict[str, Any]:
             pass
     now = m.app_now()
     active_count = m.get_active_position_count(conn)
-    can_trade_trend = (
-        m.trading_day_reset_allows_new_open(now)
-        and active_count < cfg["max_active_positions"]
-        and trend_active == 0
+    from daily_open_limit_lib import can_trade_new_open, count_opens_for_trading_day
+
+    trading_day = m.get_trading_day(now)
+    opens_today = count_opens_for_trading_day(conn, trading_day)
+    hard_limit = int(getattr(m, "DAILY_OPEN_HARD_LIMIT", 0) or 0)
+    can_trade_trend = can_trade_new_open(
+        time_allows=m.trading_day_reset_allows_new_open(now),
+        active_count=active_count,
+        max_active_positions=cfg["max_active_positions"],
+        opens_today=opens_today,
+        hard_limit=hard_limit,
+        extra_blocks=trend_active != 0,
     )
     trend_preview = None
     trend_preview_levels = []