feat: trend pullback preview TP per DCA leg with unified stop loss across exchanges

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

hub_bridge.py

@@ -594,12 +594,26 @@ def _fetch_preview(pid):
     now_ms = int(time.time() * 1000)
     d["expires_in_sec"] = max(0, int((int(d.get("expires_at_ms") or 0) - now_ms) / 1000))
     try:
-        grid = json.loads(d.get("grid_prices_json") or "[]")
-        legs = json.loads(d.get("leg_amounts_json") or "[]")
+        from strategy_trend_lib import build_trend_preview_level_rows
+
+        enriched, level_rows = build_trend_preview_level_rows(d)
+        for key in ("preview_target_rr", "preview_first_take_profit", "preview_unified_stop_loss"):
+            if key in enriched:
+                d[key] = enriched[key]
+        d["preview_level_rows"] = level_rows
         d["grid_levels"] = [
-            {"i": i + 1, "price": grid[i], "contracts": legs[i] if i < len(legs) else None}
-            for i in range(len(grid))
+            {
+                "i": row.get("i"),
+                "label": row.get("label"),
+                "price": row.get("price"),
+                "contracts": row.get("contracts"),
+                "avg_entry": row.get("avg_entry"),
+                "take_profit": row.get("take_profit"),
+                "stop_loss": row.get("stop_loss"),
+            }
+            for row in level_rows
         ]
     except Exception:
         d["grid_levels"] = []
+        d["preview_level_rows"] = []
     return d