Add products, inventory units, stock receipts, and price history

- product table (catalog definition, no cost column — cost tracked
  per receipt/unit)
- inventory_unit table (serialized items with serial number,
  condition, status)
- stock_receipt table (FIFO cost tracking — records every stock
  receive event with cost_per_unit, supplier, date)
- price_history table (logs every retail price change for margin
  analysis over time)
- product_supplier join table (many-to-many, tracks supplier SKU
  and preferred supplier)
- Full CRUD routes + search (name, SKU, UPC, brand)
- Inventory unit routes nested under products
- Price changes auto-logged on product update
- 33 tests passing

packages/shared/src/schemas/inventory.schema.ts

@@ -25,3 +25,48 @@ export type SupplierCreateInput = z.infer<typeof SupplierCreateSchema>
 
 export const SupplierUpdateSchema = SupplierCreateSchema.partial()
 export type SupplierUpdateInput = z.infer<typeof SupplierUpdateSchema>
+
+export const ItemCondition = z.enum(['new', 'excellent', 'good', 'fair', 'poor'])
+export const UnitStatus = z.enum(['available', 'sold', 'rented', 'in_repair', 'retired'])
+
+export const ProductCreateSchema = z.object({
+  sku: z.string().max(100).optional(),
+  upc: z.string().max(100).optional(),
+  name: z.string().min(1).max(255),
+  description: z.string().optional(),
+  brand: z.string().max(255).optional(),
+  model: z.string().max(255).optional(),
+  categoryId: z.string().uuid().optional(),
+  locationId: z.string().uuid().optional(),
+  isSerialized: z.boolean().default(false),
+  isRental: z.boolean().default(false),
+  isDualUseRepair: z.boolean().default(false),
+  price: z.number().min(0).optional(),
+  minPrice: z.number().min(0).optional(),
+  rentalRateMonthly: z.number().min(0).optional(),
+  qtyOnHand: z.number().int().min(0).default(0),
+  qtyReorderPoint: z.number().int().min(0).optional(),
+})
+export type ProductCreateInput = z.infer<typeof ProductCreateSchema>
+
+export const ProductUpdateSchema = ProductCreateSchema.partial()
+export type ProductUpdateInput = z.infer<typeof ProductUpdateSchema>
+
+export const ProductSearchSchema = z.object({
+  q: z.string().min(1).max(255),
+})
+
+export const InventoryUnitCreateSchema = z.object({
+  productId: z.string().uuid(),
+  locationId: z.string().uuid().optional(),
+  serialNumber: z.string().max(255).optional(),
+  condition: ItemCondition.default('new'),
+  status: UnitStatus.default('available'),
+  purchaseDate: z.string().date().optional(),
+  purchaseCost: z.number().min(0).optional(),
+  notes: z.string().optional(),
+})
+export type InventoryUnitCreateInput = z.infer<typeof InventoryUnitCreateSchema>
+
+export const InventoryUnitUpdateSchema = InventoryUnitCreateSchema.omit({ productId: true }).partial()
+export type InventoryUnitUpdateInput = z.infer<typeof InventoryUnitUpdateSchema>