Use regex to strip all trailing year suffixes before adding the canonical
one, preventing duplication like 'Show (2021) (2021) (2021)'.
- Add regex pattern (\s*\(\d{4}\))+\s*$ to remove all existing year suffixes
- Ensure idempotent behavior across multiple folder rename runs
- Add 7 unit tests covering the bug cases and edge scenarios
Fixes: 86 Eighty Six (2021) (2021)..., Alma-chan (2025) (2025)...