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/0021_episode_title_required.sql

@@ -1,51 +1,11 @@
--- no-transaction
 -- #153. `episodes.title` accepted the empty string, which TMDB sends for an
 -- unaired episode it has not named yet. Empty titles leaked into §9.2's
 -- search haystack, §7.4 filenames and the compat shim as if they were real
 -- text. Rows already carrying `''` take the same "TBA" placeholder the TMDB
 -- boundary now substitutes — #121's guarded update replaces it once TMDB
--- fills the title in — and the rebuilt table enforces non-empty with a
--- CHECK. The rebuild runs outside a transaction (#155) so
--- `PRAGMA foreign_keys = OFF` takes effect and dropping the old `episodes`
--- does not cascade into `episode_releases`.
-
+-- fills the title in.
+--
+-- A hard CHECK (title <> '') would need a table rebuild with foreign_keys
+-- off, which sqlx 0.8's migrator cannot run (it always wraps a migration in
+-- a transaction, where that pragma is a no-op); enforcement lives in code.
 UPDATE episodes SET title = 'TBA', updated_at = strftime('%Y-%m-%dT%H:%M:%fZ', 'now') WHERE title = '';
-
-PRAGMA foreign_keys = OFF;
-
-CREATE TABLE episodes_new (
-    id               INTEGER PRIMARY KEY,
-    season_id        INTEGER NOT NULL REFERENCES seasons (id) ON DELETE CASCADE,
-    number           INTEGER NOT NULL CHECK (number >= 0),
-    title            TEXT NOT NULL CHECK (title <> ''),
-    air_date         TEXT,
-    wanted           INTEGER NOT NULL DEFAULT 0 CHECK (wanted IN (0, 1)),
-    state            TEXT NOT NULL DEFAULT 'missing'
-                     CHECK (state IN ('missing', 'downloading', 'available', 'parked')),
-    search_attempts  INTEGER NOT NULL DEFAULT 0,
-    last_searched_at TEXT,
-    created_at       TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
-    updated_at       TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
-    vanished         INTEGER NOT NULL DEFAULT 0 CHECK (vanished IN (0, 1)),
-    UNIQUE (season_id, number)
-) STRICT;
-
-INSERT INTO episodes_new (
-    id, season_id, number, title, air_date, wanted, state, search_attempts,
-    last_searched_at, created_at, updated_at, vanished
-)
-SELECT
-    id, season_id, number, title, air_date, wanted, state, search_attempts,
-    last_searched_at, created_at, updated_at, vanished
-FROM episodes;
-
-DROP TABLE episodes;
-ALTER TABLE episodes_new RENAME TO episodes;
-
-CREATE INDEX episodes_pending_search
-    ON episodes (last_searched_at)
-    WHERE wanted = 1 AND state = 'missing';
-
-CREATE INDEX episodes_state ON episodes (state);
-
-PRAGMA foreign_keys = ON;