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/f5cbb673-8696-4dad-a63c-3a802ba53fd3/product.json

@@ -0,0 +1,35 @@
+{
+  "id": "f5cbb673-8696-4dad-a63c-3a802ba53fd3",
+  "slug": "phone-case",
+  "label": "Phone Case",
+  "description": "Slim flexible case with edge-to-edge print.",
+  "category": "Accessories",
+  "options": [],
+  "sizes": [
+    {
+      "id": "4be821c2-8ba5-4dd1-ad0b-1a188dd89796",
+      "slug": "generic",
+      "label": "Generic Wrap",
+      "physical": {
+        "width": 2.7,
+        "height": 5.4,
+        "unit": "in"
+      },
+      "canvas": {
+        "width": 270,
+        "height": 540
+      },
+      "printZone": {
+        "x": 27,
+        "y": 54,
+        "width": 216,
+        "height": 432
+      },
+      "silhouettePath": "M27,0 L243,0 A27,27 0 0 1 270,27 L270,513 A27,27 0 0 1 243,540 L27,540 A27,27 0 0 1 0,513 L0,27 A27,27 0 0 1 27,0 Z",
+      "mockupFallbackColor": "#e0e7ff",
+      "basePriceCents": 2200
+    }
+  ],
+  "createdAt": "2026-05-25T12:31:21.563Z",
+  "updatedAt": "2026-05-25T12:31:21.563Z"
+}