fix(file): verify target folder ownership on move

When moving a file to a folder, verify that the caller owns the target
folder. Without this check, a file could be moved to another user's
folder, causing the file to "disappear" from the original user's view
since file listings filter by user_id.

- Add folder_repo to FileManagementService
- Add verify_target_folder_owner() method
- Call it in move_file_owned() before moving

src/common/di.rs

@@ -261,6 +261,7 @@ impl AppServiceFactory {
             repos.file_write_repository.clone(),
             trash_service.clone(),
             Some(repos.file_read_repository.clone()),
+            Some(repos.folder_repository.clone()),
             Some(core.thumbnail_service.clone()),
         ));