feat(automation): expose group title and allow setting secondary text

Surface {{groupNow.*}} template variables (title, note, colour, times,
custom fields) in the automation template autocomplete so events inside a
group can reference their group. The runtime store already carries
groupNow, so substitution and filters worked already; this makes it
discoverable.

Extend the message-secondary action with an optional text field so an
automation can set the secondary message content, not just its source.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LZYPZVdZLWowU7DyzGkWyy

apps/server/src/api-data/automation/clients/ontime.client.ts

@@ -66,6 +66,7 @@ export function toOntimeAction(action: OntimeAction) {
         timer: {
           secondarySource: action.secondarySource,
         },
+        secondary: action.text,
       });
       break;
     }