fix: round website rates to two decimals

backend/app/utils/number.py

@@ -1,7 +1,7 @@
 """Shared numeric formatting utilities."""
 from __future__ import annotations
 
-from decimal import Decimal, InvalidOperation
+from decimal import Decimal, InvalidOperation, ROUND_HALF_UP
 from typing import Any
 
 
@@ -23,3 +23,20 @@ def decimal_string(value: Any) -> str:
     if n == n.to_integral():
         return str(n.quantize(Decimal("1")))
     return format(n, "f")
+
+
+def fixed_decimal_string(value: Any, places: int = 2) -> str:
+    """Format a numeric value with a fixed number of decimal places."""
+    if value is None or value == "":
+        return ""
+    try:
+        d = Decimal(str(value))
+    except (InvalidOperation, ValueError):
+        return str(value)
+    quantum = Decimal("1").scaleb(-places)
+    return format(d.quantize(quantum, rounding=ROUND_HALF_UP), f".{places}f")
+
+
+def fixed_decimal_number(value: Any, places: int = 2) -> float:
+    """Round a numeric value to a fixed precision for JSON number payloads."""
+    return float(fixed_decimal_string(value, places))