Quote every template block in the Site vars

The deploy failed on 'YAML parsing failed: missing quotes around a template
block'. vars/hopsngrains.yml had been edited to derive its names from the web
address, but the two derived values were unquoted and YAML reads a leading brace
as a flow mapping, so the file did not parse at all.

The names now derive from a title (the domain) with every interpolation quoted,
which is what nginx-menu did and what makes the file copyable for another Site:
host menu.<title>, container menu-app.<title>, network <container>_net, data
/var/lib/menu-app.<title>. Resolving the vars offline gives exactly the values
the docs promise, including /app/config/hopsngrains.site.json inside the image.

The old edit derived from host, so app_root would have been
/var/lib/menu.hopsngrains.com — the directory the old static menus were served
from.

ansible/vars/hopsngrains.yml

@@ -2,10 +2,15 @@
 # Hops n Grains. Its name, tagline, icon, categories and menus live on the
 # server under app_root and are edited in the admin; config/hopsngrains.site.json
 # only seeds the theme. This file says where the Site runs and what it answers.
-host: menu.hopsngrains.com
+#
+# Every value that interpolates a template is quoted: YAML reads a leading `{`
+# as a flow mapping, which is the parse error Ansible reports as "missing quotes
+# around a template block".
+title: hopsngrains.com
+host: 'menu.{{ title }}'
 
-docker_container: menu-app.hopsngrains.com
+docker_container: 'menu-app.{{ title }}'
 docker_network: '{{ docker_container }}_net'
 
 # Everything the app writes — data/ and the untracked site.env.
-app_root: /var/lib/menu-app.hopsngrains.com
+app_root: '/var/lib/menu-app.{{ title }}'