Cleaned up general back end code. Removed few overlapping features, fixed sizing of scaling errors. Added arrows to easily switch between weeks without need to open calendar view.

Updated code to correctly display date without needing to refresh extension.

Custom Week Offset Settings: Introducing a new "Options" panel, accessible via a small gear icon at the bottom right of the popup. You can now:
- Enable/Disable Offset: Choose to apply a custom offset to your week numbers.
- Set Custom Offset Value: Easily add or subtract weeks (e.g., +1, -2) to suit your specific tracking needs. By
default, new installations will have a +2 offset enabled.

Dark Mode Support: A new sun/moon toggle button has been added to the bottom left of the popup. Click it to switch between light and dark themes, making the extension more comfortable to use in various lighting conditions. Your dark mode preference will be saved.

Enhanced Calendar Interaction: The calendar will no longer unexpectedly collapse when you click outside of it. It will now only close when you press the "-" (collapse) button in the top bar, providing a smoother user experience.