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/95dca14e-28e4-46e8-93b1-b45e3b556530/product.json

@@ -0,0 +1,58 @@
+{
+  "id": "95dca14e-28e4-46e8-93b1-b45e3b556530",
+  "slug": "poster",
+  "label": "Poster",
+  "description": "Premium matte poster, suitable for framing.",
+  "category": "Wall Art",
+  "options": [],
+  "sizes": [
+    {
+      "id": "7d015072-f884-4e04-8a39-ce7c8e149059",
+      "slug": "12x18",
+      "label": "12\" × 18\"",
+      "physical": {
+        "width": 12,
+        "height": 18,
+        "unit": "in"
+      },
+      "canvas": {
+        "width": 1200,
+        "height": 1800
+      },
+      "printZone": {
+        "x": 120,
+        "y": 180,
+        "width": 960,
+        "height": 1440
+      },
+      "silhouettePath": "M48,0 L1152,0 A48,48 0 0 1 1200,48 L1200,1752 A48,48 0 0 1 1152,1800 L48,1800 A48,48 0 0 1 0,1752 L0,48 A48,48 0 0 1 48,0 Z",
+      "mockupFallbackColor": "#f3f4f6",
+      "basePriceCents": 1800
+    },
+    {
+      "id": "9a5529fd-e54e-4868-acbb-5a62c44d1297",
+      "slug": "18x24",
+      "label": "18\" × 24\"",
+      "physical": {
+        "width": 18,
+        "height": 24,
+        "unit": "in"
+      },
+      "canvas": {
+        "width": 1800,
+        "height": 2400
+      },
+      "printZone": {
+        "x": 180,
+        "y": 240,
+        "width": 1440,
+        "height": 1920
+      },
+      "silhouettePath": "M72,0 L1728,0 A72,72 0 0 1 1800,72 L1800,2328 A72,72 0 0 1 1728,2400 L72,2400 A72,72 0 0 1 0,2328 L0,72 A72,72 0 0 1 72,0 Z",
+      "mockupFallbackColor": "#e5e7eb",
+      "basePriceCents": 2400
+    }
+  ],
+  "createdAt": "2026-05-25T12:31:21.556Z",
+  "updatedAt": "2026-05-25T12:31:21.556Z"
+}