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

deploy/README.md

@@ -0,0 +1,75 @@
+# Deployment
+
+Two independent deployments share the same codebase and Docker image build:
+
+| env  | container             | backend domain                  | install target                                   | partner-dashboard app   | shopify config           |
+| ---- | --------------------- | ------------------------------- | ------------------------------------------------ | ----------------------- | ------------------------ |
+| dev  | `linumiq-invoice-dev` | `invoice-app-dev.linumiq.com`   | `linumiq-dev.myshopify.com`                      | `linumiq-invoice-dev`   | `shopify.app.dev.toml`   |
+| prod | `linumiq-invoice-prod`| `invoice-app.linumiq.com`       | `5aiizq-ti.myshopify.com` (= `shop.linumiq.com`) | `linumiq-invoice` (prod)| `shopify.app.prod.toml`  |
+
+## Server layout (root server)
+
+```
+/docker/linumiq-invoice/
+├── git/                       # checkout of this repo (git pull here)
+├── dev/
+│   ├── docker-compose.yml     # symlink → ../git/deploy/docker-compose.dev.yml
+│   ├── .env.dev               # secrets (NOT in git)
+│   └── data/                  # bind-mounted SQLite + cached assets
+└── prod/
+    ├── docker-compose.yml     # symlink → ../git/deploy/docker-compose.prod.yml
+    ├── .env.prod              # secrets (NOT in git)
+    └── data/                  # bind-mounted SQLite + cached assets
+```
+
+Both containers attach to the external `caddy_net` Docker network. Caddy reverse-proxies each subdomain to the correct container by name (see `Caddyfile.snippet`).
+
+## First-time setup on the server
+
+```bash
+sudo mkdir -p /docker/linumiq-invoice/{git,dev/data,prod/data}
+sudo chown -R "$USER" /docker/linumiq-invoice
+
+cd /docker/linumiq-invoice
+git clone git@git.linumiq.com:LinumIQ/linumiq-invoice.git git
+
+# DEV
+cd /docker/linumiq-invoice/dev
+ln -s ../git/deploy/docker-compose.dev.yml docker-compose.yml
+cp ../git/deploy/.env.dev.example .env.dev   # then edit secrets
+docker compose up -d --build
+
+# PROD
+cd /docker/linumiq-invoice/prod
+ln -s ../git/deploy/docker-compose.prod.yml docker-compose.yml
+cp ../git/deploy/.env.prod.example .env.prod   # then edit secrets
+docker compose up -d --build
+```
+
+Append `Caddyfile.snippet` to your Caddy config and `docker exec caddy caddy reload --config /etc/caddy/Caddyfile`.
+
+## Day-to-day redeploy
+
+```bash
+cd /docker/linumiq-invoice/git && git pull
+cd /docker/linumiq-invoice/dev  && docker compose up -d --build   # update dev
+cd /docker/linumiq-invoice/prod && docker compose up -d --build   # update prod
+```
+
+Run only the env you want to update.
+
+## Pushing config / extension changes to Shopify
+
+From your dev machine (after `git pull` to keep configs in sync):
+
+```bash
+# DEV  → linumiq-dev.myshopify.com
+npx shopify app config use shopify.app.dev.toml
+npx shopify app deploy --allow-updates
+
+# PROD → shop.linumiq.com
+npx shopify app config use shopify.app.prod.toml
+npx shopify app deploy --allow-updates
+```
+
+The currently selected config is stored in `.shopify/project.json` (gitignored), so each developer machine remembers its own choice.