Use SQLite as a fallback for MySQL in case it can't connect to the database

We should use SQLite as a fallback in the event that MySQL has a connection error.

When MySQL is properly configured, it can import everything from the SQLite database and do some kind of reconciliation.

No files, tests, or entry points are named. Start by tracing the existing MySQL and SQLite storage configuration and connection handling, then clarify what reconciliation should mean and how a connection failure is detected. Done criteria should specify fallback behavior, import direction, and how conflicting data is resolved.

Written by the indexing model from the issue text.