feat: 0.1.1 — timeline scrubber, gallery virtualisation, folder reorder, QoL polish

Timeline:
- Add a right-edge scrubber (year labels + month dots) that jumps to any
  period; runs in the same direction as the scrolled content
- Load the full filtered set in Timeline view so the scrubber spans the whole
  library instead of just the first page

Gallery & UI:
- Virtualise the gallery grid
- Folder reordering in the sidebar (drag + persisted sort_order) and a themed
  dropdown component
- Subtle Light theme contrast fixes for toggles, secondary buttons and the
  update toast

Embedding workers now defer video jobs without a thumbnail at claim time and
requeue any previously-failed deferred jobs on startup, so videos no longer
churn through failed embeddings.

QoL polish across BackgroundTasks, DuplicateFinder, Lightbox and VideoPlayer.

src-tauri/src/embedder.rs

@@ -221,8 +221,8 @@ fn load_images(paths: &[PathBuf], image_size: usize) -> Result<Tensor> {
 /// Returns the path that should be fed to the CLIP image embedder for a given media file.
 ///
 /// For videos the thumbnail image is used (because CLIP only understands still images).
-/// If a video has no thumbnail yet, an error is returned — the caller should mark the
-/// embedding job as failed rather than trying to decode the raw video file.
+/// Video jobs without thumbnails are excluded when jobs are claimed. The error remains
+/// as a guard against a race where a thumbnail disappears after a job is claimed.
 pub fn embedding_source_path(
     path: &str,
     thumbnail_path: Option<&str>,