Fix CI version test sentinel: wait for 'Time Zone:' not 'borgmatic'

The borgmatic wrapper now prints a WARNING containing 'borgmatic' before
s6 init completes. The CI test was polling for 'borgmatic' in logs as a
readiness signal, which fired immediately on the warning — before
svc-cron/run had printed the version table.

'Time Zone:' only appears at the end of the version table, making it a
reliable sentinel that the container is fully initialised.

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

Author: modem7

.github/workflows/CI.yml

@@ -307,7 +307,7 @@ jobs:
         run: |
           docker run -d --name test-versions -e CRON=false ${{ env.IMAGE }}
           timeout 30 bash -c \
-            'until docker logs test-versions 2>&1 | grep -q "borgmatic"; do sleep 1; done'
+            'until docker logs test-versions 2>&1 | grep -q "Time Zone:"; do sleep 1; done'
           logs=$(docker logs test-versions 2>&1)
           echo "$logs"
           echo "$logs" | grep -qE "borg [0-9]"       || { echo "borg version missing";       exit 1; }