Seed the dev store's collections from a production snapshot

The AFK half of the wayfinder ticket "Seed the dev store from the live
catalogue". Products, metafields and images still come from the CSV export —
the CSV re-hosts images for free — but collection membership cannot: the
Collection column is import-only, takes one collection per product, and this
catalogue runs 1.6 memberships per product across 16 collections.

- scripts/seed-dev-store.mjs (`npm run seed:dev-store`): creates each missing
  collection with its members in one call and publishes it. Uses
  CollectionCreateInput.sources because collectionAddProducts is deprecated at
  2026-10, and publishes because collectionCreate leaves a collection
  unpublished — invisible to the Storefront API the dev store exists to serve.
  Idempotent, never deletes, reports handles it cannot find (which is how a
  partial CSV import shows up), and is a dry run unless given --apply.
- assets/dev-store-seed.json: the baseline the seed is checked against and the
  membership map it consumes — 61 products with option values, weights and
  product types, 16 collections with 100 memberships, and the 10 metafield
  definitions that must exist before the import.
- The ticket now records what the probes settled: the option shape is readable
  from the Storefront API (all 61 use Option1 name=Title; 22 are `Default
  Title`, 39 carry real values, so the import must not normalise), and the
  repo's production credentials are Storefront-scoped only — `products`,
  `collections` and `productsCount` are Access denied without read_products —
  so the ticket's "Admin API script using the credentials the repo already
  mints" was never available. A dev-store custom app is required instead.

package.json

@@ -14,7 +14,8 @@
     "lint": "eslint . && prettier --check .",
     "format": "prettier --write .",
     "pb": "bash -c 'if [ ! -f .pb/pocketbase ]; then mkdir -p .pb && curl -sL -o .pb/pb.zip https://github.com/pocketbase/pocketbase/releases/download/v0.40.2/pocketbase_0.40.2_linux_amd64.zip && (cd .pb && unzip -o -q pb.zip pocketbase && rm pb.zip); fi; cd .pb && ./pocketbase serve --http=127.0.0.1:8090 --dir=./pb_data'",
-    "seed": "node --env-file-if-exists=.env scripts/pb-seed.mjs"
+    "seed": "node --env-file-if-exists=.env scripts/pb-seed.mjs",
+    "seed:dev-store": "node --env-file-if-exists=.env scripts/seed-dev-store.mjs"
   },
   "dependencies": {
     "@sentry/tanstackstart-react": "^10.73.0",