ci: stop the stale bot from closing relevant issues

days-before-stale was 7, so any discussion thread got nagged after a
week. exempt-issue-labels pointed at a 'Postpone' label that did not
exist in the repo, so nothing was ever exempt, and PRs had no exemption
list at all.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DrPGBtLDkdnYXQv4u3r7bG

Author: Kikobeats

.github/workflows/stale-issues.yml

@@ -24,8 +24,10 @@ jobs:
 
           stale-issue-label: 'stale'
 
-          days-before-stale: 7
+          days-before-stale: 60
 
           days-before-close: 7
 
-          exempt-issue-labels: 'Postpone'
+          exempt-issue-labels: 'Postpone, next-version'
+
+          exempt-pr-labels: 'Postpone, next-version'