fix: add failed tag locate and filter controls

Add a failed-tag discovery flow for background worker failures.

Changes:
- Add a Failed Tags toolbar filter that appears when tag failures exist.
- Add Locate buttons for failed tag tasks in the background worker prompt.
- Route Locate to the affected folder and filter the gallery to images with tagger errors.
- Fetch and display failed tag filenames/errors in the expanded worker details.
- Add a backend query and gallery filter flag for images with failed AI tagging.
- Improve subtle-light contrast for failed worker chips, filenames, and Locate/Retry buttons.
- Also slightly increases the title bar update indicator pulse size for better visibility.

src-tauri/src/commands.rs

@@ -38,6 +38,7 @@ pub struct GetImagesParams {
     pub favorites_only: Option<bool>,
     pub rating_min: Option<i64>,
     pub embedding_failed_only: Option<bool>,
+    pub tagging_failed_only: Option<bool>,
     pub sort: Option<String>,
     pub offset: Option<i64>,
     pub limit: Option<i64>,
@@ -329,6 +330,7 @@ pub async fn get_images(
     let favorites_only = params.favorites_only.unwrap_or(false);
     let rating_min = params.rating_min.unwrap_or(0);
     let embedding_failed_only = params.embedding_failed_only.unwrap_or(false);
+    let tagging_failed_only = params.tagging_failed_only.unwrap_or(false);
 
     let total = db::count_images(
         &conn,
@@ -338,6 +340,7 @@ pub async fn get_images(
         favorites_only,
         rating_min,
         embedding_failed_only,
+        tagging_failed_only,
     )
     .map_err(|e| e.to_string())?;
 
@@ -349,6 +352,7 @@ pub async fn get_images(
         favorites_only,
         rating_min,
         embedding_failed_only,
+        tagging_failed_only,
         sort,
         offset,
         limit,
@@ -594,6 +598,34 @@ pub async fn retry_failed_embeddings(
     db::retry_failed_embedding_jobs(&conn, params.folder_id).map_err(|e| e.to_string())
 }
 
+#[derive(Serialize)]
+pub struct FailedImageItem {
+    pub image_id: i64,
+    pub filename: String,
+    pub path: String,
+    pub error: Option<String>,
+}
+
+#[tauri::command]
+pub async fn get_failed_tagging_images(
+    db: State<'_, DbState>,
+    folder_id: i64,
+) -> Result<Vec<FailedImageItem>, String> {
+    let conn = db.get().map_err(|e| e.to_string())?;
+    db::get_failed_tagging_images(&conn, folder_id)
+        .map(|rows| {
+            rows.into_iter()
+                .map(|(image_id, filename, path, error)| FailedImageItem {
+                    image_id,
+                    filename,
+                    path,
+                    error,
+                })
+                .collect()
+        })
+        .map_err(|e| e.to_string())
+}
+
 #[tauri::command]
 pub async fn semantic_search_images(
     db: State<'_, DbState>,