Mount host zoneinfo into runner for TZ support (#160)

## Summary

The `TZ=America/Los_Angeles` env var from #159 has no effect because the `forgejo/runner` image doesn't ship tzdata. Mount the node's `/usr/share/zoneinfo` into the container so the timezone database is available.

## Deployment

After merge, sync forgejo-runner and verify:
```
argocd app sync forgejo-runner
kubectl -n forgejo-runner exec deploy/forgejo-runner -c runner -- date
# Should show PST/PDT, not UTC
```

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/160

argocd/manifests/forgejo-runner/deployment.yaml

@@ -56,6 +56,9 @@ spec:
               mountPath: /data
             - name: config
               mountPath: /config
+            - name: zoneinfo
+              mountPath: /usr/share/zoneinfo
+              readOnly: true
 
         # Docker-in-Docker sidecar
         - name: dind
@@ -77,3 +80,7 @@ spec:
         - name: config
           configMap:
             name: forgejo-runner-config
+        - name: zoneinfo
+          hostPath:
+            path: /usr/share/zoneinfo
+            type: Directory