chore: add cron trigger to Feature Planner (every 30 min) (#96)

User-filed issues only get the bug/feature label from templates — they
need the Feature Planner to triage and add status:backlog before the
Bug Fixer or Feature Builder can pick them up. Without a cron trigger,
issues sit in limbo until someone manually runs the planner.

Co-authored-by: Ona <no-reply@ona.com>

Author: zacharias-ona

.ona/automations/feature-planner.yaml

@@ -1,6 +1,12 @@
 name: Feature Planner
 description: Triages unlabeled issues, decomposes product-spec into backlog items, and ensures issue quality.
 triggers:
+    - context:
+        projects:
+            projectIds:
+                - 019d8bf4-1ded-7317-be2f-555e8fb55ff9
+      time:
+        cronExpression: "*/30 * * * *"
     - context:
         projects:
             projectIds: