Copy GitHub releases onto Gitea mirrors

Gitea drops releases for pull mirrors, so a new cron/manual workflow
creates releases for tags already synced to Gitea, updates edited
notes, and streams missing assets. Adds a README.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/sync-releases.yml

@@ -0,0 +1,34 @@
+name: Sync releases to Gitea
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '30 */4 * * *' # Every 4 hours, 30 min after the mirror run
+
+concurrency:
+  group: sync-releases
+
+jobs:
+  releases:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 24
+      - name: Copy GitHub releases to Gitea mirrors
+        id: sync
+        run: node sync-releases.js
+        env:
+          GH_PAT: ${{ secrets.GH_PAT }}
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          GITEA_URL: ${{ secrets.GITEA_URL }}
+
+      - name: Notify via ntfy
+        if: ${{ always() }}
+        run: node notify.js
+        env:
+          NTFY_TOPIC_URL: ${{ secrets.NTFY_TOPIC_URL }}
+          WORKFLOW_KIND: releases
+          STEP_OUTCOME: ${{ steps.sync.outcome }}
+          RUN_URL: https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}