feat: add Docker setup and CI workflows for headless server

.gitea/workflows/docker-build.yml

@@ -0,0 +1,29 @@
+name: Build and push Docker image (Gitea)
+
+on:
+  push:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/setup-buildx-action@v3
+      - uses: docker/login-action@v3
+        with:
+          registry: git.byte-mate.ru
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.GITEA_TOKEN }}
+      - uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: |
+            git.byte-mate.ru/Coder/UfaHack2024:latest
+            git.byte-mate.ru/Coder/UfaHack2024:${{ gitea.sha }}
+
+# Notes:
+#   - Create the GITEA_TOKEN secret in the Gitea repository settings.
+#   - A Gitea Actions runner must be registered on the server for this
+#     workflow to run.