chore: add UNNECESSARY_FILES.md to .gitignore

- Remove UNNECESSARY_FILES.md from git tracking
- Add to .gitignore as internal analysis file
- File will remain locally but not be tracked in repository

Author: T-DevH

.gitignore

@@ -173,3 +173,6 @@ test_*.py
 !**/test_*.py
 !**/*_test.py
 !tests/test_basic.py
+
+# Documentation - Internal analysis files
+UNNECESSARY_FILES.md