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/common/di.rs

@@ -263,7 +263,8 @@ impl AppServiceFactory {
                 blob_backend,
                 db_pool.clone(),
                 maintenance_pool.clone(),
-            ),
+            )
+            .with_thumbnail_service(thumbnail_service.clone()),
         );
         dedup_service.initialize().await?;
 
@@ -981,6 +982,48 @@ pub struct CoreServices {
     pub config: AppConfig,
 }
 
+impl CoreServices {
+    /// Invalidate a file's moka thumbnail cache and kick off background regeneration.
+    ///
+    /// Call this after any write that swaps the blob for an existing file.
+    /// Safe to call for new files too (no-op on empty cache).
+    /// Skips everything if the MIME type is not a supported image.
+    pub async fn refresh_thumbnails_after_update(
+        &self,
+        file_id: String,
+        blob_hash: String,
+        content_type: &str,
+    ) {
+        if !ThumbnailService::is_supported_image(content_type) {
+            return;
+        }
+        if let Err(e) = self.thumbnail_service.delete_thumbnails(&file_id).await {
+            tracing::warn!(
+                "Failed to invalidate thumbnail cache for {}: {}",
+                file_id,
+                e
+            );
+        }
+        let ts = self.thumbnail_service.clone();
+        let ds = self.dedup_service.clone();
+        let hash = blob_hash.clone();
+        tokio::spawn(async move {
+            match ds.read_blob_bytes(&hash).await {
+                Ok(bytes) => {
+                    ts.generate_all_sizes_background_from_bytes(file_id, hash, bytes);
+                }
+                Err(e) => {
+                    tracing::warn!(
+                        "Failed to read blob for thumbnail regeneration {}: {}",
+                        file_id,
+                        e
+                    );
+                }
+            }
+        });
+    }
+}
+
 /// Container for repository services
 #[derive(Clone)]
 pub struct RepositoryServices {