Refactor badge views to remove Matplotlib and use Pillow for image ge…

…neration

This commit introduces several improvements to the badge views:
- Replaced Matplotlib with Pillow for generating badge images
- Removed Matplotlib and related dependencies from pyproject.toml
- Implemented a custom badge image generation using Pillow
- Added comprehensive tests for badge views in website/tests/test_badge_views.py
- Improved visit tracking logic for project and repo badges
- Enhanced badge image with more detailed visualization of visit data