Host the action on Gitea

Workflows move to .gitea/workflows, which Gitea prefers over
.github/workflows when both exist.

GitHub Actions can only resolve `uses:` against github.com, so the
README now spells out both forms: the full Gitea URL, and the
checkout-then-`uses: ./` fallback for a GitHub workflow that has no
mirror of this repository.

examples/manual-promote.yml

@@ -22,7 +22,7 @@ jobs:
     environment: ${{ inputs.environment }}
     steps:
       - id: deploy
-        uses: maxvojtkov/dokploy-deploy-action@v1
+        uses: https://gitea.coolify.vojtkov.dev/usr_unknown/dokploy-deploy-action@v1
         with:
           host: ${{ secrets.DOKPLOY_HOST }}
           api-key: ${{ secrets.DOKPLOY_API_KEY }}