0.6.1: low risk security update

Updated yt-dlp dependency to require version 2026.2.21 or newer. Previous versions had a vulnerability in netrc_cmd handling (GHSA-g3gw-q23r-pgqm, CVE-2026-26331). Yanki does not use netrc, and thus was not affected, but I upgraded out of an abundance of caution.

0.6.0: Flashcard web UI

• Added flashcard web UI so that decks can be used without Anki.
• Added experimental automatic video trimming with trim: auto.
• Fixed a few race conditions; in particular slicing up a long video into many flashcards now avoids a condition that could cause significant slow-downs.
• Cleaned up CLI commands.

v0.5.1

Release 0.5.1: Fix links on PyPi.