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.dev.toml

@@ -0,0 +1,42 @@
+# Learn more about configuring your app at https://shopify.dev/docs/apps/tools/cli/configuration
+
+client_id = "fbc263e6cc28e8de031878d2a0f17444"
+application_url = "https://invoice-app-dev.linumiq.com"
+embedded = true
+name = "linumiq-invoice-dev"
+
+[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-dev.linumiq.com/auth/callback",
+  "https://invoice-app-dev.linumiq.com/auth/shopify/callback",
+  "https://invoice-app-dev.linumiq.com/api/auth/callback",
+]
+
+[build]
+automatically_update_urls_on_dev = true