bugfix/thumbnails on update

Bug 1 & 2 (webdav_handler.rs handle_put() update branch):
  - After a successful file update via WebDAV PUT, if the content type is a supported image:
    a. delete_thumbnails(file_id) — evicts the stale moka cache entry
    b. Spawns a background task to read the new blob bytes and call generate_all_sizes_background_from_bytes

  Bug 3 & 4 (dedup_service.rs):
  - Added thumbnail_service: Option<Arc<ThumbnailService>> field with a with_thumbnail_service() builder
  - In remove_legacy_reference(): calls delete_blob_thumbnails(hash) when ref_count hits 0
  - In remove_manifest_reference(): calls delete_blob_thumbnails(file_hash) when manifest's last ref is dropped
  - Wired in di.rs — the thumbnail service is created before dedup service so the ordering works cleanly

src/interfaces/api/handlers/webdav_handler.rs

@@ -972,6 +972,15 @@ async fn handle_put(
                 );
             }
 
+            state
+                .core
+                .refresh_thumbnails_after_update(
+                    file_dto.id.clone(),
+                    file_dto.etag.clone(),
+                    &content_type,
+                )
+                .await;
+
             Ok(Response::builder()
                 .status(StatusCode::NO_CONTENT)
                 .body(Body::empty())