User-supplied asset ids; brand on product; strain is the name

Four UX changes after using the rework for a bit:

1. Asset ids are 6-digit numbers from a roll of physical labels — server
   no longer generates them. POST /api/inventory requires assetId; the
   add-inventory form has a digits-only input that auto-focuses on entry.
2. Strain and product name are the same thing. Drop products.name; the
   strain's name supplies the display. Product creation just asks for
   "Name (strain)" and matches/creates a strain by that name.
3. Brand moves from inventory_items to products. SKUs are brand-specific,
   so all instances of a product share the brand. Brand selector lives
   on the product create/edit form, not the per-instance form.
4. Scanning an unknown SKU on the add-inventory step now opens the
   create-product subform with the SKU prefilled — one less click.

Migration: detect prior shape (products.name column present) and rename
products/inventory_items/audits to *_v1 archives, recreate empty.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/src/routes/catalog.ts

@@ -35,12 +35,12 @@ catalogRouter.patch("/brands/:id", (req, res) => {
   }
 });
 
-// Deleting a brand unparents any inventory items that reference it
-// (brand_id → NULL), so users never lose inventory when reorganizing.
+// Deleting a brand unparents any products that reference it
+// (brand_id → NULL on products), so users never lose inventory.
 catalogRouter.delete("/brands/:id", (req, res) => {
   const { id } = req.params;
   const tx = db.transaction(() => {
-    db.prepare("UPDATE inventory_items SET brand_id = NULL WHERE brand_id = ?").run(id);
+    db.prepare("UPDATE products SET brand_id = NULL WHERE brand_id = ?").run(id);
     const result = db.prepare("DELETE FROM brands WHERE id = ?").run(id);
     if (result.changes === 0) throw new Error("not found");
   });