Restore `HasOne::take` and fix a formatting clippy lint

Re-add `HasOne::take` (dropped when `HasOne` was reshaped) so `has_one` code that
takes ownership of the loaded model — including the quickstart example — keeps
compiling. It maps onto the new two-variant enum via `mem::take` + `into_option`.

Also fix a pre-existing `clippy::useless_borrows_in_formatting` in
`database/statement.rs` (redundant `&` in `write!` args) that newer clippy
rejects under `-D warnings`.