GrowingGoal refactor + implementation in Admin Dashboard

[thaninbew]

This ticket is only for the GrowingGoal component within the Admin Dashboard. Design can be found on Figma HiFi.
Context: GrowingGoal exists in the Donation Page but we are reusing it in the Admin Dashboard Overview. Its values are currently hardcoded, so:

• Create a Goal entity/table to store the targets, like $50,000 for a date range.

• Implement an endpoint that returns the active goal and the calculated progress from the donations table.

• Update the current GrowingGoal component to the dynamic, non-hardcoded values.

• All of this will require further refactoring of GrowingGoal component to be more modular, since the components used between the donation page and dashboard are slightly different.

• Implement the GrowingGoal on the admin dashboard page exactly as seen on Figma, use TailwindCSS/shadcn where possible.

• Requirements: Current amount raised vs. Target goal (e.g., $31,336 of $50,000).

• Date Range: Should reflect the active goal period (e.g., "January - June 2026").