fix(arr): clear subtitle attempts on language drop

Removing a language from wanted_languages left its subtitle_attempts
rows behind, resurrecting stale backoff on re-add (#224).

.sqlx/query-0f94b0f839cfcbe4a70ee5be81f452c88dc610d05042d4af811963c0cbc6113e.json

@@ -0,0 +1,26 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT wanted_languages FROM subtitle_settings WHERE id = 1",
+  "describe": {
+    "columns": [
+      {
+        "name": "wanted_languages",
+        "ordinal": 0,
+        "type_info": "Text",
+        "origin": {
+          "Table": {
+            "table": "subtitle_settings",
+            "name": "wanted_languages"
+          }
+        }
+      }
+    ],
+    "parameters": {
+      "Right": 0
+    },
+    "nullable": [
+      false
+    ]
+  },
+  "hash": "0f94b0f839cfcbe4a70ee5be81f452c88dc610d05042d4af811963c0cbc6113e"
+}

.sqlx/query-74178ac3ec41aa8a5ce164103a8d8301cb555eea2fa5d655a7365fd02c557cce.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "DELETE FROM subtitle_attempts WHERE language = ?",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": []
+  },
+  "hash": "74178ac3ec41aa8a5ce164103a8d8301cb555eea2fa5d655a7365fd02c557cce"
+}

crates/arr-api/src/subtitle_settings.rs

@@ -196,8 +196,20 @@ pub async fn update(
 ) -> Result<Json<SubtitleSettings>, ApiError> {
     let input = parsed(body)?;
     input.validate().map_err(ApiError::Invalid)?;
+    let new_wanted = input.wanted_languages.clone();
     let columns = input.into_columns()?;
     let timeout_seconds = columns.remote_command_timeout_seconds;
+
+    let previous_wanted: String =
+        sqlx::query_scalar!("SELECT wanted_languages FROM subtitle_settings WHERE id = 1")
+            .fetch_one(pool(&state)?)
+            .await?;
+    let dropped: Vec<String> = column::<Vec<String>>("wanted_languages", &previous_wanted)?
+        .into_iter()
+        .filter(|language| !new_wanted.contains(language))
+        .collect();
+
+    let mut transaction = pool(&state)?.begin().await?;
     sqlx::query!(
         r#"UPDATE subtitle_settings SET
                wanted_languages = ?, providers_enabled = ?, translation_engine = ?,
@@ -212,8 +224,20 @@ pub async fn update(
         columns.translator_daily_budgets,
         columns.remote_command_timeout_seconds,
     )
-    .execute(pool(&state)?)
+    .execute(&mut *transaction)
     .await?;
+    // #224: a dropped language's attempt bookkeeping (backoff counter,
+    // `last_failure`) must not resurrect if the language is re-added later.
+    // Subtitle files stay — only the attempt rows are wanted-set-scoped.
+    for language in &dropped {
+        sqlx::query!(
+            "DELETE FROM subtitle_attempts WHERE language = ?",
+            language
+        )
+        .execute(&mut *transaction)
+        .await?;
+    }
+    transaction.commit().await?;
     // Issue #219: the row alone never reaches the running backend. Push it
     // into the cell the remote-command translator re-reads per batch; the
     // cell counts milliseconds, the row counts seconds.
@@ -270,6 +294,30 @@ mod tests {
         (dir, format!("http://{address}"), timeout)
     }
 
+    /// The same app, with the underlying pool exposed so a test can seed or
+    /// inspect rows the API surface does not read back directly.
+    async fn application_with_pool() -> (tempfile::TempDir, String, sqlx::SqlitePool) {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let database = arr_db::Db::connect(dir.path().join("arr.db"))
+            .await
+            .expect("connect database");
+        database.migrate().await.expect("migrate database");
+        let pool = database.pool().clone();
+        let state = AppState::new(Upstreams::new(
+            "http://127.0.0.1:1".into(),
+            "http://127.0.0.1:1".into(),
+        ))
+        .expect("state")
+        .with_database(database);
+        let listener = tokio::net::TcpListener::bind("127.0.0.1:0")
+            .await
+            .expect("bind");
+        let address = listener.local_addr().expect("address");
+        let app = router(state);
+        tokio::spawn(async move { axum::serve(listener, app).await.expect("serve") });
+        (dir, format!("http://{address}"), pool)
+    }
+
     fn valid_input() -> serde_json::Value {
         serde_json::json!({
             "wanted_languages": ["pt-PT", "en"],
@@ -334,6 +382,53 @@ mod tests {
         assert_eq!(refetched, updated);
     }
 
+    /// #224: dropping a language from `wanted_languages` must clear its
+    /// `subtitle_attempts` rows — otherwise re-adding it later resurrects a
+    /// stale backoff counter as though the attempts had just happened.
+    #[tokio::test]
+    async fn dropping_a_language_clears_its_attempt_rows() {
+        let (_dir, base, pool) = application_with_pool().await;
+        sqlx::query(
+            "INSERT INTO media_files (id, owner_kind, owner_id, path, size)
+             VALUES (1, 'movie', 1, 'x.mkv', 1)",
+        )
+        .execute(&pool)
+        .await
+        .expect("media file");
+        sqlx::query(
+            "INSERT INTO subtitle_attempts
+                 (media_file_id, language, state, attempts, last_attempt_at, last_failure)
+             VALUES (1, 'en', 'failed', 3, '2024-01-01T00:00:00Z', 'no provider match')",
+        )
+        .execute(&pool)
+        .await
+        .expect("dropped-language attempt");
+        sqlx::query(
+            "INSERT INTO subtitle_attempts (media_file_id, language, state) VALUES (1, 'pt-PT', 'wanted')",
+        )
+        .execute(&pool)
+        .await
+        .expect("kept-language attempt");
+
+        let mut payload = valid_input();
+        payload["wanted_languages"] = serde_json::json!(["pt-PT"]);
+        reqwest::Client::new()
+            .put(format!("{base}/api/settings/subtitles"))
+            .json(&payload)
+            .send()
+            .await
+            .expect("put settings")
+            .error_for_status()
+            .expect("valid input accepted");
+
+        let remaining: Vec<String> =
+            sqlx::query_scalar("SELECT language FROM subtitle_attempts ORDER BY language")
+                .fetch_all(&pool)
+                .await
+                .expect("attempts");
+        assert_eq!(remaining, vec!["pt-PT".to_string()]);
+    }
+
     /// Issue #219: the row alone never reaches the running backend, so a PUT
     /// must push its value into the cell the command translator re-reads.
     #[tokio::test]