docs: short readme

template/caddy/README.md.jinja

@@ -1,23 +1,5 @@
 {%- set dash = project_slug | replace('_', '-') -%}
+{%- set domain = project_slug | upper | replace('-', '_') ~ '_DOMAIN' -%}
 # caddy
 
-`site.caddy` routes `{{ '{$' }}{{ project_slug | upper | replace('-', '_') }}_DOMAIN}` to the project's services over the external `caddy` docker network. It works standalone and inside a shared Caddy that fronts several projects.
-
-Standalone:
-
-```sh
-docker network create caddy
-cp Caddyfile.example Caddyfile
-cp .env.example .env
-docker compose up -d
-```
-
-Shared Caddy: mount this directory as `/etc/caddy/projects.d/{{ dash }}:ro`, keep `import /etc/caddy/projects.d/*/site.caddy` in its Caddyfile and put `{{ project_slug | upper | replace('-', '_') }}_DOMAIN` in its environment.
-
-Rules that keep `site.caddy` portable:
-
-- the domain comes only from the environment variable
-- no `tls` block, certificates are configured by the host Caddy (`acme_dns cloudflare {env.CLOUDFLARE_API_TOKEN}` in the global block)
-- snippets are prefixed with the project slug because Caddy snippets are global
-- mount the directory, not the file: a single-file bind mount goes stale when git replaces the inode
-- keep `admin localhost:2019`, `admin off` makes `caddy reload` impossible
+`site.caddy` routes `{{ '{$' }}{{ domain }}}` to the project over the external `caddy` network. In a shared Caddy, mount this directory as `/etc/caddy/projects.d/{{ dash }}:ro` and set `{{ domain }}`. Keep it portable: domain only from the env, no `tls`, snippets prefixed with `{{ project_slug }}_`.