fix(renovate): pin action to a real tag (v46.1.15)

renovatebot/github-action ships only full semver tags; @v40 was an
invalid ref and the dispatched run failed to resolve it.

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

.gitea/workflows/renovate.yml

@@ -18,7 +18,9 @@ jobs:
     runs-on: docker
     steps:
       - name: Run Renovate
-        uses: renovatebot/github-action@v40
+        # This action publishes only full semver tags (no moving major tag —
+        # @v46 / @v40 etc. 404). Pin a real release; Renovate keeps it bumped.
+        uses: renovatebot/github-action@v46.1.15
         env:
           # Self-hosted Gitea, not github.com.
           RENOVATE_PLATFORM: gitea