Add Gitea Actions CI/CD pipeline

Build and push images to the private registry, then deploy to the VPS by commit SHA with health check and rollback.

docker-compose.build.yaml

@@ -0,0 +1,14 @@
+# Local-dev override: restores the build context that docker-compose.yaml gave up
+# when deploys moved to registry images.
+#
+#   docker compose -f docker-compose.yaml -f docker-compose.build.yaml up -d --build
+#
+# CI does not use this file — the deploy workflow builds with `docker build`
+# directly so it can tag and push in one step.
+services:
+  ksan-dev:
+    build:
+      context: .
+      args:
+        PLANS_PAGES: ${PLANS_PAGES}
+    image: ${IMAGE_NAME:-git.ksan.dev/ksan/ksan.dev}:${IMAGE_TAG:-dev}