theres no other functionality except the basic car backfill lol

- remove sqlx cache bc i aint usin it rn (will add it back l8r for docker build)
- document how im going to do backfill/etc
- add meta table with a rev column. this is to store repo rev for diffing/etc

we use `cargo sqlx prepare` with offline mode as the database can be offline when docker starts, which leads to builds failing