done with backend performance improvement

[sivakornchong]

Requests:

1. Use a binary format for loading data faster [oak]
2. Have no redundant filtering/mutating of the data in the app [oak]
3. Create a processed data file that is loaded in the app instead (stored in data/processed). [oak]
4. Have no excessively slow computation that could be easily sped up, e.g. no row-wise use of apply unless well justified and optimized.[oak]
5. Use caching for at least one function [oak]

Done:

1. Currently converted the preprocessed file to be pickle. App loads from this preprocessed file
2. Ensured there is no redundant filtering on the preprocessed file -> See expansion to def RefreshData() to include all the preprocessing instead of running directlty on data.py.
3. Processed data file has been created.
4. No slow computation -> API not loaded every time upon start up.
5. Caching is done for get_vancouver_data(), so that if user calls it again with the same output argument (i.e. on the same day), the API query will not be repeated.

[render[bot]]

Your Render PR Server URL is https://dsci-532-2024-10-vanweather-pr-81.onrender.com.

Follow its progress at https://dashboard.render.com/web/srv-cofhg6n79t8c73ffuddg.

[sivakornchong]

Added a loading bar for refresh button too.