Refactor: Remove settings.json and cleanup tracked user files

[shaygol]

This commit includes major cleanup and improvements across the codebase:

Core Changes:

• Remove settings.json persistence mechanism (simplified configuration)
• Remove window geometry save/restore feature (simpler startup)
• Fix error reporter to ignore KeyboardInterrupt and SystemExit
• Keep dashboard.xlsx template in repo for deployment

Code Changes:

• config.py: Removed settings file functions (load/save/get/set_setting)
• gui_app.py: Removed window geometry persistence imports and logic
• error_reporter.py: Added filtering for KeyboardInterrupt/SystemExit

Documentation Updates:

• README.md: Removed references to Window Persistence
• roadmap.md: Added (replaces IMPROVEMENTS.md) with updated features list
• IMPROVEMENTS.md: Deleted (replaced by roadmap.md)

Tests:

• Added test_category_manager_robustness.py
• Added test_duplicate_detection.py
• Added test_file_deletion.py
• Removed tests/smoke/test_smoke.py (obsolete)

Git Tracking Cleanup:

• Removed UserFiles/categories.json from tracking (user's personal data)
• Removed UserFiles/backups/ from tracking (backup files)
• Removed output/budget.log from tracking (runtime logs)
• Kept UserFiles/dashboard.xlsx for deployment workflow

The application now starts with default window size (1200x800) and focuses on core functionality without unnecessary persistence overhead.