fix(sqlite): dedup clears old external id before canonical upsert

crates/adapters/sqlite/src/repositories/movie_dedup/mod.rs

@@ -37,6 +37,14 @@ impl MovieDeduplicator for SqliteMovieDeduplicator {
             .await
             .map_err(crate::shared::map_sqlx_error)?;
 
+        // The old row still holds the external id (it is deleted last); release it
+        // so the canonical upsert does not violate UNIQUE(external_metadata_id).
+        sqlx::query("UPDATE movies SET external_metadata_id = NULL WHERE id = ?")
+            .bind(&old)
+            .execute(&mut *tx)
+            .await
+            .map_err(crate::shared::map_sqlx_error)?;
+
         sqlx::query(
             "INSERT INTO movies (id, external_metadata_id, title, release_year, director, poster_path)
              VALUES (?, ?, ?, ?, ?, ?)