Add vitest specs for user-cards quantity validation, scan upload-image auth/rate-limit/MIME gates, ScannerDestinationPicker, and ScannedCardItem. Suite grows 21 → 37 tests. Co-authored-by: Cursor <cursoragent@cursor.com>
Match decks handler parseInt/NaN guard so non-numeric quantities cannot corrupt user_cards row counts from scanner add paths. Co-authored-by: Cursor <cursoragent@cursor.com>