Switch Framework to SQLite by Default

[smcintyre-r7]

Summary

Framework currently has the option of using no database (in which case the user misses out on a lot of functionality) or PostgreSQL. Using PostgreSQL requires the independent postgres service which is a source of frustration during installation and a maintenance burden.

Framework should switch to SQLite.

This work will require us to migrate to Rails 8 as a prerequisite.

Basic example

N/A

Motivation

Provide users with a consistent experience and feature set without requiring them to install the external PostgreSQL service.

[adfoster-r7]

This should build on: #19852