isNumeric static method
Numeric validation for string input
Checks if the string can be parsed as a number (int or double).
Example:
FSValidators.isNumeric('123.45'); // true
FSValidators.isNumeric('abc'); // false
Implementation
static bool isNumeric(String? value) {
if (value == null || value.isEmpty) return false;
return double.tryParse(value) != null;
}