feat: extract several marked archives at once, each into its own folder

[nextestudios]

Summary

• With archives marked, North shows Extrair cada um para a própria pasta (N) as the first option (North → South extracts). Marked items that aren't archives (by extension) are left out; the real format is still detected by content before enqueuing.
• A confirmation dialog lists each archive and the folder it will get. On confirm, each archive is enqueued through the existing extraction flow as its own operation (dedicated folder, never reusing an existing one, so contents never mix and repeated stems get "(2)"). Each keeps its own progress, cancel, retry and retry-failed in Menu → Operations and in the history.
• Passwords aren't asked up front: the queue is serial, so a protected archive fails fast with PasswordRequired and asks in its turn, one at a time; cancelling the keyboard records "senha não informada" for that archive.
• Instead of one result dialog per archive, a single summary appears when all are done, with one line per archive (completed / warnings / cancelled / failed + folder).
• GUIDE and README (both languages) and both changelogs updated.

Tested in CI

• Journey: docs.zip, fotos.zip, fotos.tar.gz (same inner file name) and a non-archive marked → the menu offers 3, three completed Extract operations, folders docs, fotos, fotos (2) each with only their own content, summary lists each archive, no folder for the text file.

Manual checks

• None beyond the usual visual review of the dialogs.

Closes #69

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