fix(trend): remove inferred DCA fill prices across all exchanges

Unify display on trend_leg_display_price: use recorded fills or grid triggers only; last done row avg comes from live entry, never back-solve trigger prices.

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

tests/test_trend_hub_enrich_unified.py

@@ -81,7 +81,9 @@ class TestTrendHubEnrichUnified(unittest.TestCase):
         self.assertIn("dca_levels", hub)
         last_done = hub["dca_levels"][2]
         self.assertEqual(last_done["status"], "done")
+        self.assertAlmostEqual(last_done["price"], 0.343, places=4)
         self.assertAlmostEqual(last_done["avg_entry"], 0.3507, places=4)
+        self.assertLess(last_done["price"], 0.36)
         self.assertEqual(hub.get("monitor_source"), "趋势回调计划")
         self.assertEqual(hub.get("add_count"), 2)