Release v0.1.18

- Changes
•	Added ExceptionCode with built-in standard codes (ISE-500, VAL-422, etc.)
•	Unified fallback errors to use ExceptionCode.INTERNAL_SERVER_ERROR
•	Improved validation error handling with consistent responses
•	Updated docs: added parameters table + clearer examples
•	Updated packaging (pyproject.toml) with Python 3.10+ requirement and project URLs

Author: akutayural