v0.13.2: Faster comment downloads + comment media links on resume

Channel comments get a major speedup and a media-link fix. Refs #80 (#85).

Highlights

• Much faster comment downloads. --comments now fetches the linked discussion group in a single date-bounded pass and maps each comment to its post by thread root, instead of one request per post. On large channels this drops the comment fetch from ~an hour to minutes.
• Comment media links now show on resume. With --comments --media --html --html-media-links, a comment's attachment (PDF, image, video, audio) is now linked in the HTML export even on resume runs over an older export that was saved without the link. Previously the file downloaded but no link appeared.

Notes

• Comment fetching no longer uses the per-post *.comments-progress.json checkpoint; resume re-maps from the resumed discussion download and de-duplicates automatically.
• No config or CLI changes required — existing flags behave the same, just faster and more complete.

Install / upgrade: pip install -U telegram-download-chat · Windows: telegram-download-chat-v0.13.2-setup.exe

Full changelog: v0.13.1...v0.13.2