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/04507704-50a9-4de9-9b23-475d6b76bf0e/product.json

@@ -0,0 +1,35 @@
+{
+  "id": "04507704-50a9-4de9-9b23-475d6b76bf0e",
+  "slug": "sticker",
+  "label": "Sticker",
+  "description": "Weatherproof vinyl sticker, die-cut to your design.",
+  "category": "Stationery",
+  "options": [],
+  "sizes": [
+    {
+      "id": "6744bd80-e64b-4351-a0b8-9316dd138db5",
+      "slug": "3in-die-cut",
+      "label": "3\" Die-Cut",
+      "physical": {
+        "width": 3,
+        "height": 3,
+        "unit": "in"
+      },
+      "canvas": {
+        "width": 300,
+        "height": 300
+      },
+      "printZone": {
+        "x": 30,
+        "y": 30,
+        "width": 240,
+        "height": 240
+      },
+      "silhouettePath": "M12,0 L288,0 A12,12 0 0 1 300,12 L300,288 A12,12 0 0 1 288,300 L12,300 A12,12 0 0 1 0,288 L0,12 A12,12 0 0 1 12,0 Z",
+      "mockupFallbackColor": "#fce7f3",
+      "basePriceCents": 400
+    }
+  ],
+  "createdAt": "2026-05-25T12:31:21.560Z",
+  "updatedAt": "2026-05-25T12:31:21.560Z"
+}