Support SQLite as a query log target

The current database backends for query logging are MySQL, PostgreSQL, and TimescaleDB. For single-node setups like a Raspberry Pi or homelab, running a separate database just for query logging is a lot of overhead. SQLite would be a good fit here since the GORM SQLite driver is already in `go.mod` and used in the `DatabaseWriter` tests. Config would just be a file path: ```yaml queryLog: type: sqlite target: /var/log/blocky/queries.db logRetentionDays: 30 ``` Happy to put together a PR if there's interest.