ci: auto-merge patch and minor renovate updates

Add a packageRule that automerges patch and minor updates, with
platformAutomerge enabled so Gitea merges them once required checks pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

renovate.json

@@ -22,8 +22,14 @@
       "description": "Commit every update as fix(deps) so each merged Renovate PR triggers a patch release. config:recommended pulls in :semanticPrefixFixDepsChoreOthers, which forces non-npm updates (Docker, Actions) to chore and would otherwise produce no release.",
       "matchPackageNames": ["*"],
       "semanticCommitType": "fix"
+    },
+    {
+      "description": "Auto-merge patch and minor updates once checks pass.",
+      "matchUpdateTypes": ["patch", "minor"],
+      "automerge": true
     }
   ],
+  "platformAutomerge": true,
   "customManagers": [
     {
       "customType": "regex",