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/lib.rs

@@ -162,6 +162,7 @@ pub fn run() {
             commands::get_explore_tags,
             commands::get_images_by_ids,
             commands::get_failed_embedding_images,
+            commands::get_failed_tagging_images,
             commands::get_tagger_model_status,
             commands::get_tagger_acceleration,
             commands::set_tagger_acceleration,