Review / Cram mode

[bootuz]

Summary

Adds a read-only Review / Cram mode — browse a deck's or folder's cards in a horizontal flip-card carousel, with no rating and no FSRS scheduling. Mirrors the iOS ReviewManager/ReviewView. This is the "study anytime" mode earmarked when we built the deck-detail "You're all caught up!" state.

• StudyQueueBuilder.buildReviewQueue now also excludes memorized cards (parity: a card memorized on iOS stays out of Android review too). buildStudyQueue is untouched — the FSRS study path is unaffected.
• ReviewViewModel snapshots the pool once (read-only): deck → its own reviewFilter + shuffled; folder → all directions across the folder's decks, always shuffled; both exclude memorized/deleted. Logs cram_session_start (named distinctly from the FSRS study session's review_session_start to avoid an analytics collision).
• ReviewScreen = a HorizontalPager of the existing FlipCard: swipe between cards, tap to flip (resets per page via remember(currentPage) + key(card.id)), "{i} of {n}" + Quit, tap-to-flip hint, empty/loading states.
• Entry points: an always-present "Review" button on deck-detail (shown whenever the deck has cards, including the all-caught-up state) and a folder-detail top-bar action; Koin registration + two nav routes (review/{deckId}, reviewFolder/{folderId}).

Out of scope (v1): rating/FSRS effects, a "mark memorized" toggle (no Android UI — synced field only), audio autoplay, an end-of-deck summary, deck-list ⋮ entry, global "review everything", per-folder filter/shuffle.

Test plan

• StudyQueueBuilderTest — buildReviewQueue excludes memorized + deleted; direction filters; shuffle determinism.
• ReviewViewModelTest (3) — deck applies its filter + excludes memorized/deleted; folder aggregates across only that folder's decks (both directions); empty deck → empty pool.
• Full unit-test suite green; :app:assembleDebug BUILD SUCCESSFUL; ReviewScreen compile-verified + previews.
• Manual smoke (pending emulator): deck "Review" button (incl. all-caught-up) → carousel; swipe + tap-to-flip; "{i} of {n}"; Quit; folder top-bar Review across decks (shuffled); empty deck/folder → "No cards to review here."; study queue/due counts unchanged afterward.

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