fix(db): drop 0.8 rebuild workarounds, enforce title

With sqlx 0.9 honouring `-- no-transaction`, 0007 loses its
movie_releases_backup stash like 0014 did, and 0021 gains
the CHECK (title <> '') that #153 abandoned because the 0.8
migrator could not run a rebuild with foreign keys off. The
rebuild test now enters at migration 6 so the child links
ride through all three rebuilds, and a new test proves the
'' -> 'TBA' backfill and the rejection of new empty titles.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/arr-db/src/lib.rs

@@ -336,7 +336,7 @@ mod tests {
         assert_eq!(renamed_from_imported, "available");
     }
 
-    /// #155: migration 0014 rebuilds `movies` and `episodes` outside a
+    /// #155: the table-rebuild migrations (0007, 0014, 0021) run outside a
     /// transaction so `PRAGMA foreign_keys = OFF` holds and dropping the old
     /// tables does not cascade-delete `movie_releases`/`episode_releases`.
     #[tokio::test]
@@ -347,9 +347,9 @@ mod tests {
             .expect("connect");
 
         MIGRATOR
-            .run_to(13, db.pool())
+            .run_to(6, db.pool())
             .await
-            .expect("migrations before the 0014 rebuild");
+            .expect("migrations before the first rebuild");
 
         sqlx::query(
             "INSERT INTO movies (tmdb_id, title, root_id)
@@ -419,6 +419,55 @@ mod tests {
         );
     }
 
+    /// #153: an empty episode title takes the TBA placeholder during 0021's
+    /// backfill, and the rebuilt table's CHECK rejects new empty titles.
+    #[tokio::test]
+    async fn empty_episode_titles_are_backfilled_and_then_rejected() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let db = Db::connect(dir.path().join("arr.db"))
+            .await
+            .expect("connect");
+
+        MIGRATOR
+            .run_to(20, db.pool())
+            .await
+            .expect("migrations before the #153 backfill");
+
+        let series_id = sqlx::query(
+            "INSERT INTO series (tmdb_id, title, root_id)
+             SELECT 82728, 'Bluey', id FROM roots WHERE kind = 'tv' LIMIT 1",
+        )
+        .execute(db.pool())
+        .await
+        .expect("series")
+        .last_insert_rowid();
+        let season_id = sqlx::query("INSERT INTO seasons (series_id, number) VALUES (?, 1)")
+            .bind(series_id)
+            .execute(db.pool())
+            .await
+            .expect("season")
+            .last_insert_rowid();
+        sqlx::query("INSERT INTO episodes (season_id, number, title) VALUES (?, 1, '')")
+            .bind(season_id)
+            .execute(db.pool())
+            .await
+            .expect("empty title, valid before 0021");
+
+        db.migrate().await.expect("remaining migrations");
+
+        let title: String = sqlx::query_scalar("SELECT title FROM episodes")
+            .fetch_one(db.pool())
+            .await
+            .expect("episode row survives the rebuild");
+        assert_eq!(title, "TBA");
+
+        sqlx::query("INSERT INTO episodes (season_id, number, title) VALUES (?, 2, '')")
+            .bind(season_id)
+            .execute(db.pool())
+            .await
+            .expect_err("the rebuilt column rejects the empty string");
+    }
+
     #[tokio::test]
     async fn seeds_two_tv_roots_with_distinct_policies() {
         let (_dir, db) = fresh().await;