fix(meta): store unrated titles as NULL, not zero

TMDB reports vote_average: 0 where no rating exists (#156). Normalise
it to None at the arr-meta edge, like non_empty does for "", and let
the Option flow through the daemon refresh and API add paths so the
nullable columns from #145 do their job.

crates/arr-daemon/src/grab.rs

@@ -2497,6 +2497,81 @@ mod tests {
         assert_eq!(unchanged, (poster, backdrop, vote));
     }
 
+    /// TMDB reports `vote_average: 0` for a title nobody has rated — absence,
+    /// not zero (#156). It must store as NULL, be overwritten when votes
+    /// arrive, and go back to NULL if they are withdrawn.
+    #[tokio::test]
+    async fn metadata_refresh_stores_an_unrated_title_as_null() {
+        let (_dir, database) = wanted_movie().await;
+        let indexer = empty_prowlarr().await;
+        let unrated = || {
+            RELEASED_METADATA.replace(
+                r#""original_language": "en","#,
+                r#""original_language": "en",
+                  "poster_path": "/dune-two.jpg",
+                  "backdrop_path": "/dune-two-wide.jpg",
+                  "vote_average": 0.0,"#,
+            )
+        };
+        let rated = || {
+            RELEASED_METADATA.replace(
+                r#""original_language": "en","#,
+                r#""original_language": "en",
+                  "poster_path": "/dune-two.jpg",
+                  "backdrop_path": "/dune-two-wide.jpg",
+                  "vote_average": 8.152,"#,
+            )
+        };
+        let (downloader, _fake) = transmission().await;
+
+        action_with_tmdb(&indexer, &downloader, &tmdb(&unrated()).await)
+            .tick(&database)
+            .await
+            .unwrap();
+        let vote: Option<f64> =
+            sqlx::query_scalar("SELECT vote_average FROM movies WHERE tmdb_id IS NOT NULL")
+                .fetch_one(database.pool())
+                .await
+                .unwrap();
+        assert_eq!(vote, None);
+
+        // Votes arrive: the NULL is overwritten.
+        sqlx::query(
+            "UPDATE movies SET metadata_refreshed_at = strftime('%Y-%m-%dT%H:%M:%fZ', 'now', '-7 hours')",
+        )
+        .execute(database.pool())
+        .await
+        .unwrap();
+        action_with_tmdb(&indexer, &downloader, &tmdb(&rated()).await)
+            .tick(&database)
+            .await
+            .unwrap();
+        let vote: Option<f64> =
+            sqlx::query_scalar("SELECT vote_average FROM movies WHERE tmdb_id IS NOT NULL")
+                .fetch_one(database.pool())
+                .await
+                .unwrap();
+        assert_eq!(vote, Some(8.152));
+
+        // And withdrawn again.
+        sqlx::query(
+            "UPDATE movies SET metadata_refreshed_at = strftime('%Y-%m-%dT%H:%M:%fZ', 'now', '-7 hours')",
+        )
+        .execute(database.pool())
+        .await
+        .unwrap();
+        action_with_tmdb(&indexer, &downloader, &tmdb(&unrated()).await)
+            .tick(&database)
+            .await
+            .unwrap();
+        let vote: Option<f64> =
+            sqlx::query_scalar("SELECT vote_average FROM movies WHERE tmdb_id IS NOT NULL")
+                .fetch_one(database.pool())
+                .await
+                .unwrap();
+        assert_eq!(vote, None);
+    }
+
     #[tokio::test]
     async fn metadata_changes_reset_a_title_backoff() {
         let (_dir, database) = wanted_movie().await;

crates/arr-daemon/src/series_refresh.rs

@@ -232,7 +232,7 @@ impl SeriesRefreshAction {
         let backdrop_path_ref = backdrop_path.as_deref();
         let artwork_moved =
             stale.poster_path != poster_path || stale.backdrop_path != backdrop_path;
-        if artwork_moved || stale.vote_average != Some(vote_average) {
+        if artwork_moved || stale.vote_average != vote_average {
             sqlx::query!(
                 "UPDATE series SET poster_path = ?, backdrop_path = ?, vote_average = ?,
                                         updated_at = strftime('%Y-%m-%dT%H:%M:%fZ', 'now')