chore: switch to GHCR image in docker-compose, remove dokploy webhook

- docker-compose.yml now uses pre-built ghcr.io image instead of build
- ORIGIN is configurable via env var for deployment
- Remove deploy job from release workflow (Dokploy pulls compose from repo)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -54,11 +54,3 @@ jobs:
         uses: softprops/action-gh-release@v2
         with:
           generate_release_notes: true
-
-  deploy:
-    name: Deploy
-    runs-on: ubuntu-latest
-    needs: release
-    steps:
-      - name: Trigger Dokploy redeploy
-        run: curl -X POST "${{ secrets.DOKPLOY_WEBHOOK_URL }}"