Update/improve the stats
This MR updates the Python stats calculations to:
- Handle cases with no carbon data
- Manage errors thrown by the backend and pass them to the frontend
- Streamline shapefile/polygon statistics calculation
- Add area size constraints and raise errors accordingly
- Fix returned GeoJSON issue to plot area on map
- Simplify the structure of mean values to reduce bandwidth usage
- Add raster path to the configuration file/env for flexible setup and deployment
- Implement a loading progress bar with configurable duration during statistics calculation to keep users patient during the 10-20 second wait
- Miscellaneous refactoring