KnowledgeVault AI module-spec M-02

M-02 creates the products catalog and product_pre_seeds tables, exposes GET /api/products/queue for authenticated experts, and delivers two mobile screens: the Product Queue Screen (S-02-a) where experts browse and filter SKUs by specialty, and the Product Pre-Session Screen (S-02-b) where they review product details and earnings before starting a capture session. Coverage percentage is stubbed at 0.0 in all queue responses until M-04 adds product_id tracking to capture_sessions. product_pre_see