Set TZ on build-blumeops job, not just the runner pod

The runner's TZ env var doesn't propagate to workflow job containers
(which run inside DinD). Set TZ at the job level so towncrier uses
the correct timezone when stamping changelog entries.

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

.forgejo/workflows/build-blumeops.yaml

@@ -37,6 +37,8 @@ on:
 jobs:
   build:
     runs-on: k8s
+    env:
+      TZ: America/Los_Angeles
     steps:
       - name: Resolve version
         id: version