feat: add date filters to volunteer analytics

[akankshab418]

Summary

I added separate date filters for the Volunteer Activity Trend and Volunteers by Location charts.

The Volunteer Activity Trend now supports 7D, 30D, 1Y, All, and Custom date ranges. The 7D, 30D, and Custom options group the results by day, while 1Y and All group them by month.

I also changed the trend response key from month to period.

For Volunteers by Location, I added the same date-range options, but the data is only filtered by date. I did not change the existing country grouping or response format.

The trend and location filters work independently, and the changes are applied to both the Virginia and Ireland database calls.

Testing completed

• Checked the Python syntax.
• Checked for whitespace issues.
• Tested all supported date ranges for both charts.
• Tested separate trend and location filters.
• Tested Custom start and end dates.
• Tested country and skill filters along with Custom dates.
• Tested the Virginia and Ireland merge logic.
• Used the local CSV files from the sql folder for local testing.

I did not make any changes to the existing production credential setup.