fix(db): keep migration checksums stable

Issue #155 removed the sqlx 0.8 rebuild workarounds by editing migrations
0007, 0014 and 0021 in place. Editing an applied migration changes its
checksum, and `migrate()` refuses to run when one no longer matches what
`_sqlx_migrations` recorded, so the daemon exited on startup against any
database that had already applied them — production included.

The sqlx 0.9 bump is the fix and survives: a new migration can carry
`-- no-transaction` so `PRAGMA foreign_keys = OFF` holds and a table
rebuild stops cascade-deleting its children. Only the retroactive cleanup
of migrations that already ran is reverted, along with #153's
`CHECK (title <> '')`, which rode on the 0021 edit and needs a migration
of its own rather than a rewrite of history.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/arr-db/migrations/0007_movie_state_canonical.sql

@@ -1,13 +1,13 @@
--- no-transaction
 -- #73. movies.state used missing|grabbed|imported, predating arr-core's
 -- canonical MediaState vocabulary (missing|downloading|available) that
 -- series/episodes (0005) already follow.
 --
--- SQLite can't ALTER a CHECK constraint, so this rebuilds the table. It runs
--- outside a transaction (#155) so `PRAGMA foreign_keys = OFF` takes effect
--- and dropping the old `movies` does not cascade into `movie_releases`.
+-- SQLite can't ALTER a CHECK constraint, so this rebuilds the table -- which
+-- means dropping the old copy. `movie_releases` references it with
+-- ON DELETE CASCADE, so the drop would take its rows down too; stash them
+-- first and restore them once the new `movies` exists with the same ids.
 
-PRAGMA foreign_keys = OFF;
+CREATE TABLE movie_releases_backup AS SELECT * FROM movie_releases;
 
 CREATE TABLE movies_new (
     id                INTEGER PRIMARY KEY,
@@ -68,4 +68,6 @@ BEGIN
     SELECT RAISE(ABORT, 'movies require a movie root');
 END;
 
-PRAGMA foreign_keys = ON;
+INSERT INTO movie_releases SELECT * FROM movie_releases_backup;
+
+DROP TABLE movie_releases_backup;