Set TZ on build-blumeops workflow job (#161)

## Summary

The runner pod's `TZ` env var (#159, #160) doesn't propagate to workflow job containers — jobs run inside Docker containers spawned by the DinD sidecar, not in the runner process itself. Set `TZ: America/Los_Angeles` at the job level so `uvx towncrier build` uses the correct timezone.

This is the actual fix for the Feb 12 changelog dates. The runner pod TZ is still useful for runner daemon logs but doesn't affect job execution.

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/161

.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