ci: fix calens workflow permissions for reusable workflow call

The reusable calens workflow requires `contents: read` but the caller
set `permissions: {}` (none), causing a startup_failure on every push.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: DeepDiver1975

.github/workflows/calens.yml

@@ -5,7 +5,8 @@ on:
     branches:
       - master
 
-permissions: {}
+permissions:
+  contents: read
 
 jobs:
   changelog: