feat: add full-margin position sizing mode across four exchanges

Env POSITION_SIZING_MODE switches risk vs full-margin (available*buffer, BTC/ETH 10x). Blocks trend/roll/key auto opens in full margin, purges breakout/fib monitors with WeChat notice, keeps RR check and initial SL snapshot for records.

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

strategy_register.py

@@ -103,6 +103,17 @@ def _count_active_trends(conn, cfg: dict) -> int:
 
 
 def _roll_preview_response(cfg: dict, data: dict, json_mode: bool = False) -> dict:
+    m = cfg.get("app_module")
+    if m is not None:
+        try:
+            from position_sizing_lib import OPEN_SOURCE_ROLL, assert_open_source_allowed
+
+            mode = getattr(m, "POSITION_SIZING_MODE", None) or "risk"
+            ok_src, src_msg = assert_open_source_allowed(mode, OPEN_SOURCE_ROLL)
+            if not ok_src:
+                return {"ok": False, "msg": src_msg}
+        except Exception:
+            pass
     get_db = cfg["get_db"]
     symbol = cfg["normalize_symbol_input"](data.get("symbol") or "")
     if not symbol: