feat: Batch tagging/selecting

Bulk apply tags to a folder (optionally recursive) with progress + batching limits.

No files or tests are mentioned. Start by scanning the TypeScript code for where photo tags are applied and where folder-based bulk operations are handled. Then locate any existing batch-processing or progress-reporting utilities and trace how they are wired into user actions/endpoints. Done means bulk tagging on a folder supports optional recursion, enforces batch limits, shows progress, and passes the relevant project tests or a manual end-to-end flow.

Written by the indexing model from the issue text.