Pricing tab: per-LOT row expansion with rowspan grouping

- Reorder columns: PN вендора / Описание / LOT / Кол-во / Estimate / Склад / Конкуренты / Ручная цена
- Explode multi-LOT BOM rows into individual LOT sub-rows; PN вендора + Описание use rowspan to span the group
- Rename "Своя цена" → "Ручная цена", "Проставить цены BOM" → "BOM Цена"
- CSV export reads PN/Desc/LOT from data attributes to handle rowspan offset correctly
- Document pricing tab layout contract in bible-local/02-architecture.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bible-local/02-architecture.md

@@ -48,6 +48,32 @@ Rules:
 - latest pricelist selection ignores snapshots without items;
 - auto pricelist mode stays auto and must not be persisted as an explicit resolved ID.
 
+## Pricing tab layout
+
+The Pricing tab (Ценообразование) has two tables: Buy (Цена покупки) and Sale (Цена продажи).
+
+Column order (both tables):
+
+```
+PN вендора | Описание | LOT | Кол-во | Estimate | Склад | Конкуренты | Ручная цена
+```
+
+Per-LOT row expansion rules:
+- each `lot_mappings` entry in a BOM row becomes its own table row with its own quantity and prices;
+- `baseLot` (resolved LOT without an explicit mapping) is treated as the first sub-row with `quantity_per_pn` from `_getRowLotQtyPerPN`;
+- when one vendor PN expands into N LOT sub-rows, PN вендора and Описание cells use `rowspan="N"` and appear only on the first sub-row;
+- a visual top border (`border-t border-gray-200`) separates each vendor PN group.
+
+Vendor price attachment:
+- `vendorOrig` and `vendorOrigUnit` (BOM unit/total price) are attached to the first LOT sub-row only;
+- subsequent sub-rows carry empty `data-vendor-orig` so `setPricingCustomPriceFromVendor` counts each vendor PN exactly once.
+
+Controls terminology:
+- custom price input is labeled **Ручная цена** (not "Своя цена");
+- the button that fills custom price from BOM totals is labeled **BOM Цена** (not "Проставить цены BOM").
+
+CSV export reads PN вендора, Описание, and LOT from `data-vendor-pn`, `data-desc`, `data-lot` row attributes to bypass the rowspan cell offset problem.
+
 ## Configuration versioning
 
 Configuration revisions are append-only snapshots stored in `local_configuration_versions`.