Dependency hardening: pin minimum safe dependency versions

Hi, thanks for bilingual_book_maker. Low-priority dependency-hardening note, not an active vulnerability report - a default install resolves to safe versions today.

These declarations also permit older versions with known CVEs; pinning a minimum prevents an accidental downgrade (please test compatibility):

• requests: pin >= 2.32.4 (e.g. CVE-2014-1829 and 2 more)
• tqdm: pin >= 4.11.2 (e.g. CVE-2016-10075)

(Low-priority dependency-hygiene note - feel free to close if not useful, happy to send a PR.)