fix: 微信支付元转分改用 Decimal，修复 2.01 元被收 2 元

utils/money.py

@@ -0,0 +1,30 @@
+"""金额换算：禁止 float 参与元/分转换（避免 2.01 元变成 200 分）。"""
+from decimal import Decimal, InvalidOperation, ROUND_HALF_UP
+
+TWO_PLACES = Decimal('0.01')
+ONE_FEN = Decimal('1')
+
+
+def to_decimal(amount) -> Decimal:
+    if amount is None:
+        return Decimal('0')
+    if isinstance(amount, Decimal):
+        return amount
+    try:
+        return Decimal(str(amount))
+    except (InvalidOperation, ValueError, TypeError):
+        return Decimal('0')
+
+
+def quantize_yuan(amount) -> Decimal:
+    return to_decimal(amount).quantize(TWO_PLACES, rounding=ROUND_HALF_UP)
+
+
+def yuan_to_fen(amount) -> int:
+    """人民币元 → 微信支付整数分（四舍五入到分）。"""
+    fen = quantize_yuan(amount) * 100
+    return int(fen.quantize(ONE_FEN, rounding=ROUND_HALF_UP))
+
+
+def format_yuan(amount) -> str:
+    return f'{quantize_yuan(amount):.2f}'