deploy: split into dev/prod with separate Shopify configs and containers

- shopify.app.toml -> shopify.app.dev.toml (domain: invoice-app-dev.linumiq.com)
- New shopify.app.prod.toml will be created via shopify app config link --config prod
- docker-compose split into deploy/docker-compose.{dev,prod}.yml with distinct
  container names (linumiq-invoice-{dev,prod}), images, env files and bind mounts
- Caddyfile snippet maps both subdomains to their respective containers
- .env.{dev,prod}.example templates committed in deploy/
- deploy/README.md documents the layout and day-to-day workflow

shopify.app.toml

@@ -1,42 +0,0 @@
-# Learn more about configuring your app at https://shopify.dev/docs/apps/tools/cli/configuration
-
-client_id = "fbc263e6cc28e8de031878d2a0f17444"
-application_url = "https://invoice-app.linumiq.com"
-embedded = true
-name = "linumiq-invoice"
-
-[access_scopes]
-# Read orders + customers + companies (B2B) for invoice data.
-# read_files / write_files for the generated PDFs uploaded to Shopify Files.
-# write_orders required to write the order metafield linking the latest PDF.
-# read_all_orders allows access to orders older than 60 days for backfill.
-scopes = "read_orders,write_orders,read_all_orders,read_customers,read_companies,read_files,write_files"
-
-[webhooks]
-api_version = "2026-07"
-
-  [[webhooks.subscriptions]]
-  uri = "/webhooks/app/uninstalled"
-  topics = [ "app/uninstalled" ]
-
-  [[webhooks.subscriptions]]
-  uri = "/webhooks/app/scopes_update"
-  topics = [ "app/scopes_update" ]
-
-  [[webhooks.subscriptions]]
-  uri = "/webhooks/orders/create"
-  topics = [ "orders/create" ]
-
-  [[webhooks.subscriptions]]
-  uri = "/webhooks/orders/updated"
-  topics = [ "orders/updated" ]
-
-[auth]
-redirect_urls = [
-  "https://invoice-app.linumiq.com/auth/callback",
-  "https://invoice-app.linumiq.com/auth/shopify/callback",
-  "https://invoice-app.linumiq.com/api/auth/callback",
-]
-
-[build]
-automatically_update_urls_on_dev = true