feat: initial commit — storefront, convex backend, and shared packages

Completes the first milestone of The Pet Loft ecommerce platform:
- apps/storefront: full customer-facing Next.js app with HeroUI (cart,
  checkout, orders, wishlist, product detail, shop, search, auth)
- convex/: serverless backend with schema, queries, mutations, actions,
  HTTP routes, Stripe/Shippo integrations, and co-located tests
- packages/types, packages/utils, packages/convex: shared workspace packages

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/convex/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "@repo/convex",
+  "version": "0.0.1",
+  "private": true,
+  "main": "./src/index.ts",
+  "types": "./src/index.ts",
+  "exports": {
+    ".": "./src/index.ts",
+    "./provider": "./src/provider.tsx"
+  },
+  "dependencies": {
+    "@repo/types": "*",
+    "convex": "*"
+  },
+  "peerDependencies": {
+    "react": ">=19.0.0"
+  }
+}