Customer accounts, order tracking, and purchase reviews (#8)

## Summary
- Slim the public contact form to email, interest, and message. Name, phone, and address live on the customer profile instead.
- Customers can register, sign in, save shipping details, and view order history. Logged-in checkout creates a Stripe Customer and saves cards on Stripe (`setup_future_usage`); we only store `stripe_customer_id`.
- Shipment tracking: EasyPost tracker lookup + webhook, plus paste-in numbers from Pirate Ship/Shippo. Customers see carrier status on their orders; `dispatch_due` refreshes open shipments.
- Product reviews (1–5) only after a paid/fulfilled purchase of that product.

Fixes #7

## Test plan
- [ ] Contact form submits with only email + message; extra name/phone/address fields are ignored
- [ ] Register, sign in, save profile (name/phone/shipping)
- [ ] Guest checkout still works; after signup, prior orders with that email show in history
- [ ] Logged-in checkout prefills shipping and does not collect card data locally
- [ ] Portal: buy label or paste a Pirate Ship tracking number, confirm status/events; customer order page shows tracking
- [ ] Product page: non-buyers cannot review; buyers can leave one 1–5 star review
- [ ] Non-staff users hitting `/portal/` redirect to `/account/`

Reviewed-on: #8

.env.prod.example

@@ -77,6 +77,8 @@ POS_API_TOKEN=
 
 # Optional when FEATURE_SHIPPING=true (also requires FEATURE_SHOP)
 EASYPOST_API_KEY=
+# Optional. If set, EasyPost tracker webhooks must send it as X-Webhook-Secret or ?token=.
+EASYPOST_WEBHOOK_SECRET=
 SHIP_FROM_LINE1=
 SHIP_FROM_CITY=
 SHIP_FROM_STATE=