feat(order): show estimated RR before open across four exchanges

Add shared manual_order_rr_preview.js to fetch order_defaults after symbol and TP/SL inputs complete, display estimated profit-loss ratio before submit in price and percentage modes (and fixed RR), unified for risk and full-margin sizing.

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

tests/test_manual_order_rr_preview.py

@@ -0,0 +1,39 @@
+"""预估盈亏比（前端 manual_order_rr_preview.js）公式与后端 calc_rr_ratio 口径一致。"""
+
+
+def _calc_rr(direction: str, entry: float, sl: float, tp: float):
+    if entry <= 0 or sl <= 0 or tp <= 0:
+        return None
+    if direction == "short":
+        risk = sl - entry
+        reward = entry - tp
+    else:
+        risk = entry - sl
+        reward = tp - entry
+    if risk <= 0 or reward <= 0:
+        return None
+    return round(reward / risk, 4)
+
+
+def _calc_rr_from_pct(sl_pct: float, tp_pct: float):
+    if sl_pct <= 0 or tp_pct <= 0:
+        return None
+    return tp_pct / sl_pct
+
+
+def test_long_price_mode_rr():
+    assert _calc_rr("long", 100.0, 95.0, 110.0) == 2.0
+
+
+def test_short_price_mode_rr():
+    assert _calc_rr("short", 100.0, 105.0, 90.0) == 2.0
+
+
+def test_invalid_geometry_returns_none():
+    assert _calc_rr("long", 100.0, 105.0, 110.0) is None
+    assert _calc_rr("short", 100.0, 95.0, 98.0) is None
+
+
+def test_pct_mode_rr():
+    assert _calc_rr_from_pct(2.0, 4.0) == 2.0
+    assert _calc_rr_from_pct(1.5, 3.0) == 2.0