fix: five PR review bugs and folder-recovery UX for missing/renamed folders

BackgroundTasks: dismiss no longer calls clearTaggingJobs; dismissal only
updates local dismissed state

DuplicateFinder: entering the view clears stale groups when the stored scan
scope differs from selectedFolderId; duplicateScanFolderId is recorded on
each scan and cache load so scope is always tracked

Tagger threshold: set_tagger_threshold now sets TAGGER_SESSION_DIRTY so the
worker rebuilds its WdTagger instance and applies the new threshold on the
next batch

Region search global scope: fetch offset+limit+2 candidates before removing
the source image so has_more is accurate across pages

Region search pagination: loadMoreImages now sets loadingImages and checks
galleryRequestToken before appending results, preventing duplicate pages and
stale responses corrupting a new collection

Folder recovery: when index_folder detects a missing path it records the
error in a new folders.scan_error column (ensure_column migration) and emits
done without deleting images, preserving them for recovery. A new
update_folder_path command rewrites image paths in the DB before reindexing
so thumbnails and embeddings are not needlessly regenerated for unchanged
files. The sidebar shows an amber warning icon on affected folders and a
recovery banner with Locate Folder and Remove actions

src-tauri/src/commands.rs

@@ -325,6 +325,37 @@ pub async fn reindex_folder(
     Ok(())
 }
 
+#[tauri::command]
+pub async fn update_folder_path(
+    app: AppHandle,
+    db: State<'_, DbState>,
+    folder_id: i64,
+    new_path: String,
+) -> Result<(), String> {
+    let new_path_buf = PathBuf::from(&new_path);
+    if !new_path_buf.is_dir() {
+        return Err(format!("Path is not a valid directory: {}", new_path));
+    }
+    let new_name = new_path_buf
+        .file_name()
+        .map(|n| n.to_string_lossy().to_string())
+        .unwrap_or_else(|| new_path.clone());
+    {
+        let conn = db.get().map_err(|e| e.to_string())?;
+        // Fetch the old path before updating so image paths can be rewritten.
+        let old_path = db::get_folders(&conn)
+            .map_err(|e| e.to_string())?
+            .into_iter()
+            .find(|f| f.id == folder_id)
+            .map(|f| f.path)
+            .ok_or("Folder not found")?;
+        db::update_folder_path(&conn, folder_id, &old_path, &new_path, &new_name)
+            .map_err(|e| e.to_string())?;
+    }
+    indexer::index_folder(app, db.inner().clone(), folder_id, new_path_buf);
+    Ok(())
+}
+
 #[tauri::command]
 pub async fn find_similar_images(
     db: State<'_, DbState>,
@@ -403,9 +434,10 @@ pub async fn find_similar_by_region(
         )
         .map_err(|e| e.to_string())?,
         None => {
-            let mut ids = vector::search_image_ids_by_embedding(&conn, &embedding, offset + limit + 1)
+            // Fetch one extra candidate to compensate for the source image that
+            // will be removed, so has_more is accurate and results span multiple pages.
+            let mut ids = vector::search_image_ids_by_embedding(&conn, &embedding, offset + limit + 2)
                 .map_err(|e| e.to_string())?;
-            // Exclude the source image from global results
             ids.retain(|&id| id != params.image_id);
             ids
         }