feat(db): store poster, backdrop and rating on titles

§9.6 keeps rich detail out of the database except for the three fields
pure-SQL views need. Adds poster_path, backdrop_path and vote_average to
movies and series, written by the daily metadata refresh in both lanes
and filled at add time from the TMDB response the create flows already
fetch.

crates/arr-db/migrations/0022_title_artwork.sql

@@ -0,0 +1,11 @@
+-- §9.6: the three fields rich detail keeps out of the database are the ones
+-- pure-SQL views need — the in-library half of unified search (§9.2) and the
+-- library grid would otherwise cost one TMDB call per row. Nullable, no
+-- default: a title added before its first metadata refresh has no artwork
+-- yet, and TMDB itself has entries with no poster.
+ALTER TABLE movies ADD COLUMN poster_path TEXT;
+ALTER TABLE movies ADD COLUMN backdrop_path TEXT;
+ALTER TABLE movies ADD COLUMN vote_average REAL;
+ALTER TABLE series ADD COLUMN poster_path TEXT;
+ALTER TABLE series ADD COLUMN backdrop_path TEXT;
+ALTER TABLE series ADD COLUMN vote_average REAL;

crates/arr-db/src/lib.rs

@@ -228,6 +228,38 @@ mod tests {
         }
     }
 
+    /// §9.6: the stored artwork columns are nullable, and `REAL` is a valid
+    /// STRICT type — a rating must not be squeezed into an integer.
+    #[tokio::test]
+    async fn title_artwork_columns_are_nullable_and_take_reals() {
+        let (_dir, db) = fresh().await;
+
+        sqlx::query(
+            "INSERT INTO movies (tmdb_id, title, root_id)
+             SELECT 1, 'No Artwork Yet', id FROM roots WHERE kind = 'movie' LIMIT 1",
+        )
+        .execute(db.pool())
+        .await
+        .expect("row without artwork");
+        sqlx::query(
+            "UPDATE movies SET poster_path = '/dune.jpg', backdrop_path = '/dune-wide.jpg',
+                    vote_average = 8.152
+             WHERE tmdb_id = 1",
+        )
+        .execute(db.pool())
+        .await
+        .expect("artwork write");
+
+        let (poster, backdrop, vote): (Option<String>, Option<String>, Option<f64>) =
+            sqlx::query_as("SELECT poster_path, backdrop_path, vote_average FROM movies")
+                .fetch_one(db.pool())
+                .await
+                .expect("movie row");
+        assert_eq!(poster.as_deref(), Some("/dune.jpg"));
+        assert_eq!(backdrop.as_deref(), Some("/dune-wide.jpg"));
+        assert_eq!(vote, Some(8.152));
+    }
+
     #[tokio::test]
     async fn foreign_keys_are_enforced() {
         let (_dir, db) = fresh().await;