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Stock (PRD 5.2): a branch's stock of a product is now the sum of its StockMovement rows. Every movement names the document that caused it and (type, refId) is unique, so replaying a sale, retrying a transfer or a second M-Pesa callback never moves the same stock twice. - Cash sales and confirmed M-Pesa payments deduct stock; purchases of a catalogue product add it. - POST /api/stock/transfers moves stock between two branches (owner: any two; manager: out of their own) and refuses to send more than the sending branch holds. Double submits are applied once. - POST /api/stock/adjustments records opening stock, breakage or a physical count (the ledger is corrected to the counted number). - GET /api/stock returns every branch x product with LOW/OUT flags (per-product lowStockThreshold, default 10); GET /api/stock/movements is the history. Sync (PRD 5.3/5.5): POST /api/transactions/cash now returns a result per sale - saved, duplicate or rejected - instead of silently skipping replays. The old client never learned a replayed sale had synced, so rows piled up until the batch passed the 100-sale limit and every flush failed with 400. Also: - A sale can hold several products (one Transaction per line, grouped by saleId); the old single-product payload is still accepted. - One bad sale is rejected on its own instead of failing the batch. - A queued sale is only accepted from the cashier who recorded it, and stays with the branch where it happened. - A product deactivated while offline is still recorded at its price; an invalid phone is dropped rather than losing the sale; the phone is now optional for cash sales. - The price the device showed is kept and a difference is flagged (priceMismatch) instead of being silently overwritten. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>