v0.6: template-manager owns the product catalog

The host no longer carries a runtime product catalog. products.js
shrinks to a legacy single-product stub; the canonical catalog lives in
template-manager's productsStore, seeded ONCE on first boot from the
new seedProducts.js (after that the store under templates/ is
authoritative and the seed is ignored — intentional, so restarts never
rewrite an admin-managed catalog). phoneModels.js and
templateCategories.js are the supporting constant sets, and
docs/template-schema.md documents the v4 schema.

templates/ is the admin-managed store itself (_products_index.json +
products/<id>/product.json, JSON only) — committed so the configured
catalog (sizes, pricing, options built up in the admin UI) survives a
fresh checkout rather than regressing to the seed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

templates/products/c722b19b-d6c6-4639-b0eb-dec34731e50d/product.json

@@ -0,0 +1,35 @@
+{
+  "id": "c722b19b-d6c6-4639-b0eb-dec34731e50d",
+  "slug": "pillow",
+  "label": "Throw Pillow",
+  "description": "Plush throw pillow with hidden zipper and insert.",
+  "category": "Home",
+  "options": [],
+  "sizes": [
+    {
+      "id": "22d04708-d964-4cdc-a682-fa9c02372a88",
+      "slug": "18x18",
+      "label": "18\" × 18\"",
+      "physical": {
+        "width": 18,
+        "height": 18,
+        "unit": "in"
+      },
+      "canvas": {
+        "width": 1800,
+        "height": 1800
+      },
+      "printZone": {
+        "x": 180,
+        "y": 180,
+        "width": 1440,
+        "height": 1440
+      },
+      "silhouettePath": "M162,0 L1638,0 A162,162 0 0 1 1800,162 L1800,1638 A162,162 0 0 1 1638,1800 L162,1800 A162,162 0 0 1 0,1638 L0,162 A162,162 0 0 1 162,0 Z",
+      "mockupFallbackColor": "#dcfce7",
+      "basePriceCents": 2400
+    }
+  ],
+  "createdAt": "2026-05-25T12:31:21.558Z",
+  "updatedAt": "2026-05-25T12:31:21.558Z"
+}