进一步修复 SQLite 并发锁冲突，统一连接与重试机制。

新增 db_conn 模块、缓存 schema 初始化、positions 页 commit，风控读库自动重试。

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

fee_specs.py

@@ -8,6 +8,8 @@ from typing import Optional
 
 from contract_specs import get_contract_spec
 
+from db_conn import connect_db
+
 DB_PATH = os.path.join(os.path.dirname(os.path.abspath(__file__)), "futures.db")
 DATA_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "data")
 DEFAULT_JSON = os.path.join(DATA_DIR, "fee_rates.json")
@@ -32,9 +34,7 @@ def product_from_code(ths_code: str) -> str:
 
 
 def _get_db():
-    conn = sqlite3.connect(DB_PATH)
-    conn.row_factory = sqlite3.Row
-    return conn
+    return connect_db()
 
 
 def get_fee_multiplier() -> float: