fix: resolve clippy warnings and rustfmt issues for CI compliance

Fix all clippy lints (collapsible if, clone on Copy, needless borrow,
redundant bindings, unused params) and apply rustfmt across the codebase.
Update test mocks to match Uuid-based trait signatures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/application/services/trash_service.rs

@@ -566,10 +566,10 @@ impl TrashUseCase for TrashService {
 
                         // Best-effort thumbnail cleanup — thumbnails are cache
                         // artifacts, so failure must not block file deletion.
-                        if let Some(thumb) = &self.thumbnail_service {
-                            if let Err(e) = thumb.delete_thumbnails(&file_id).await {
-                                warn!("Failed to delete thumbnails for file {}: {}", file_id, e);
-                            }
+                        if let Some(thumb) = &self.thumbnail_service
+                            && let Err(e) = thumb.delete_thumbnails(&file_id).await
+                        {
+                            warn!("Failed to delete thumbnails for file {}: {}", file_id, e);
                         }
                     }
                     TrashedItemType::Folder => {