Add Dockerfiles and CI pipeline for Docker build/push

- Dockerfile.cli: multi-stage build for exploredns CLI tool
- Dockerfile.web: multi-stage build for the HTTP API/web server
- Both use golang:1.24-alpine builder + alpine:3.21 final image
- CI pipeline docker job builds and pushes to gitea.hansenits.com.au registry on push to main/master

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: multica-agent <github@multica.ai>

.gitea/workflows/ci.yml

@@ -33,3 +33,37 @@ jobs:
 
       - name: Build
         run: go build -v ./...
+
+  docker:
+    runs-on: ubuntu-latest
+    needs: test
+    if: github.event_name == 'push'
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to registry
+        uses: docker/login-action@v3
+        with:
+          registry: gitea.hansenits.com.au
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      - name: Build and push CLI image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile.cli
+          push: true
+          tags: |
+            gitea.hansenits.com.au/hits/exploredns-cli:latest
+            gitea.hansenits.com.au/hits/exploredns-cli:${{ github.sha }}
+
+      - name: Build and push web image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile.web
+          push: true
+          tags: |
+            gitea.hansenits.com.au/hits/exploredns-web:latest
+            gitea.hansenits.com.au/hits/exploredns-web:${{ github.sha }}

Dockerfile.cli

@@ -0,0 +1,20 @@
+# Build stage
+FROM golang:1.24-alpine AS builder
+
+WORKDIR /src
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" -o /out/exploredns ./cmd/exploredns
+
+# Final stage
+FROM alpine:3.21
+
+RUN apk --no-cache add ca-certificates
+
+COPY --from=builder /out/exploredns /usr/local/bin/exploredns
+
+ENTRYPOINT ["exploredns"]

Dockerfile.web

@@ -0,0 +1,22 @@
+# Build stage
+FROM golang:1.24-alpine AS builder
+
+WORKDIR /src
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" -o /out/server ./cmd/server
+
+# Final stage
+FROM alpine:3.21
+
+RUN apk --no-cache add ca-certificates
+
+COPY --from=builder /out/server /usr/local/bin/server
+
+EXPOSE 8080
+
+ENTRYPOINT ["server"]