Title: Native collection export (text/CSV)

Please add a button in the Collection tab to export my full collection as text or CSV, in the same format as deck export (count, card name, set code, collector number).

Why:
- Deck export already exists, but there is no way to export what I own. Building decks outside Arena means guessing which cards I have.
- The only current options are third-party trackers that read log files, which require desktop and do not work on mobile at all. The main one-click export is behind a paid subscription.
- New players especially need this to get deckbuilding help from guides, friends, or tools without spending wildcards on cards they already own.

Suggested scope: export all, or export filtered view (by set, format, or color). Copy to clipboard like deck export, plus an optional CSV download on desktop.

Platform: works across PC, Mac, iOS, and Android.