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/1d69616b-96a8-4280-9beb-c8926222c589/product.json

@@ -0,0 +1,35 @@
+{
+  "id": "1d69616b-96a8-4280-9beb-c8926222c589",
+  "slug": "tote",
+  "label": "Tote Bag",
+  "description": "Sturdy canvas tote with reinforced straps.",
+  "category": "Accessories",
+  "options": [],
+  "sizes": [
+    {
+      "id": "61e5519d-1230-4397-a795-7303a30e0881",
+      "slug": "14x14",
+      "label": "14\" × 14\"",
+      "physical": {
+        "width": 14,
+        "height": 14,
+        "unit": "in"
+      },
+      "canvas": {
+        "width": 1400,
+        "height": 1400
+      },
+      "printZone": {
+        "x": 140,
+        "y": 140,
+        "width": 1120,
+        "height": 1120
+      },
+      "silhouettePath": "M56,0 L1344,0 A56,56 0 0 1 1400,56 L1400,1344 A56,56 0 0 1 1344,1400 L56,1400 A56,56 0 0 1 0,1344 L0,56 A56,56 0 0 1 56,0 Z",
+      "mockupFallbackColor": "#fef3c7",
+      "basePriceCents": 1800
+    }
+  ],
+  "createdAt": "2026-05-25T12:31:21.557Z",
+  "updatedAt": "2026-05-25T12:31:21.557Z"
+}