[FEATURE] Migrate backend from Firebase to Supabase

[awpala]

Is your feature request related to a problem? Please describe.
Current Firebase backend is both lackluster in performance, as well as constraining on new features development.

Describe the solution you'd like
Migrate the backend to Supabase, which provides a postgresql-based backend as a service. Note that this will require migration of full CRUD operations and the auth service, and should be done as a general "code freeze" on main (i.e., no additional front-end features development while backend refactor/migration is in progress, to avoid a "moving target" in terms of divergence of front-end features relative to changing backend API).

Describe alternatives you've considered
N/A

Additional context
This is a lower priority issue, as it will be a complicated overhaul. Creating Issue now (Dec. 2024) for documentation purposes only. To be revisited/considered again later in Summer 2025.