- Add safe_decimal() and safe_int() helper functions at module level
- Update NexusWeapon.from_api to use safe_decimal for all fields
- Update NexusArmor.from_api to use safe_decimal/safe_int
- Update NexusPlate.from_api to use safe_decimal
- Update NexusEnhancer.from_api to use safe_decimal/safe_int
- Remove duplicate safe_decimal definition
- This fixes decimal.ConversionSyntax errors from null/invalid API values