add Docker and CI/CD pipeline with ledo

Configure Next.js static export with nginx serving, Dockerfile
(multi-stage build), docker-compose for prod/dev, Gitea Actions
pipelines for build-on-push and tag-based releases using ledo tool.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/docker-build.yml

@@ -0,0 +1,27 @@
+name: Docker - build image
+run-name: ${{ gitea.actor }} builds image for project 🏗️
+on:
+  push:
+    branches:
+      - "main"
+jobs:
+  builder:
+    name: 🏗️ Docker builder (latest from master) 🏗️
+    runs-on: dind
+    steps:
+      - name: "[docker] registry login"
+        uses: docker/login-action@v2
+        with:
+          registry: git.cynarski.pl
+          username: ${{ secrets.REGISTRY_USER }}
+          password: ${{ secrets.REGISTRY_PASSWORD }}
+      - name: "[code] repository checkout"
+        uses: actions/checkout@v3
+        with:
+          submodules: recursive
+      - name: "[ledo] Image build"
+        run: ledo image build
+      - name: "[ledo] Image push"
+        run: ledo image push
+      - name: "[docker] system prune"
+        run: docker system prune -af --volumes