lazy db connections + embedded db

.gitignore

Cargo.lock

Cargo.toml

crates/back/Cargo.toml

crates/back/src/api/auth.rs

crates/back/src/api/courses.rs

crates/back/src/cli.rs

crates/back/src/db/any.rs

crates/back/src/db/mod.rs

crates/back/src/db/postgres.rs

crates/back/src/db/sled.rs

crates/back/src/main.rs

crates/back/src/util/iter_list.rs

crates/back/src/util/lazy_await.rs

crates/back/src/util/mod.rs

crates/runner/src/sandbox.rs

front