feat: make server own products

docs/server-stock-source-of-truth.md

@@ -63,16 +63,19 @@ acknowledge and ignore. Acknowledge it like any other event; it doesn't appear i
 The tablet sends `stock_set` when a product is created (unless untracked), when the default products are seeded, and
 when its stock or tracking is changed by hand.
 
-### 3. Catalog (`products` in the request)
+### 3. Catalog: managed on the dashboard
 
-- Keep upserting `name`, `category` and `priceInCents` per reported product.
-- **Ignore `stock`** in the report once the server owns the stock (keep accepting the field; older servers use it).
-- A product the server sees for the first time is created with `stock = null` (untracked). Its starting stock arrives
-  as a `stock_set` event in the same request.
-- **Stop removing products that one tablet doesn't report**: with several tablets, tablet B not knowing a product of
-  tablet A must not delete A's stock. Deleting or hiding products becomes a dashboard action (out of scope here).
-
-Process `products` **before** the events of the same request, so a `stock_set` for a new product finds it.
+- The dashboard adds, changes and archives products (archived = deleted for the tablets, kept for tabs and history).
+  A product added with a starting count is tracked from that moment.
+- The tablet's `products` report is only used on the first sync of the venue, to take over its catalog and stock once.
+  After that it is ignored, also its `stock`.
+- The sync response sends `catalog`: every product of the venue,
+  `[{ id, name, category, priceInCents, lowStockThreshold, archived }]`. The tablet adds and updates its products from
+  it, and hides archived ones and ones the catalog doesn't list (such as the default products of a newly paired
+  tablet). Leaving the key out means "the tablet manages its own catalog".
+- A paired tablet can't add, rename, reprice or delete products; it still counts stock (`stock_set`) and keeps its own
+  product pictures until pictures are managed on the dashboard.
+- A `stock_set` for a product the venue doesn't have is acknowledged and ignored.
 
 ### 4. Dashboard stock adjustments