chore(generator): add tqdm dependency for progress tracking

[kunalbhardwaj2006]

Summary

This PR introduces the tqdm dependency to support progress tracking
in the generator pipeline.

Long-running dataset generation processes currently provide limited
feedback about execution progress. Adding tqdm will allow progress
bars to be integrated into the pipeline loops.

Changes

• Added tqdm to generator/requirements.txt

Motivation

This is the first step toward improving observability of the generator
pipeline. In a follow-up change, tqdm will be integrated into the
PDF/page processing loops to provide real-time progress feedback.

Impact

No functional behavior changes yet. This prepares the project for
progress tracking improvements.

[kunalbhardwaj2006]

Hi maintainers,

While exploring the generator pipeline, I noticed that long-running
dataset generation processes do not currently show progress feedback.

This PR adds the tqdm dependency as a first step toward introducing
progress tracking in the pipeline loops.

In a follow-up update, I plan to integrate tqdm into the PDF/page
processing stages to provide real-time progress visibility.

Happy to adjust the approach if there are preferred logging or
progress tracking conventions in the project.