Add Docker support with Dockerfile, entrypoint script, and CI workflows

- Introduced a Dockerfile for building the application with Go and Node.js dependencies.
- Added a docker-entrypoint.sh script to manage container execution.
- Created a .dockerignore file to exclude unnecessary files from the Docker context.
- Updated Makefile to include a new target for building the Docker image.
- Added CI workflows for testing, formatting, and releasing artifacts in Gitea.

Dockerfile

@@ -0,0 +1,39 @@
+FROM golang:1.25-alpine AS builder
+
+WORKDIR /src
+
+# Build-time dependencies for UI and Go compilation.
+RUN apk add --no-cache nodejs npm
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY web/ui/package.json web/ui/package-lock.json ./web/ui/
+RUN npm --prefix ./web/ui ci
+
+COPY . .
+
+RUN npm --prefix ./web/ui run build
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
+    go build -trimpath -tags "netgo osusergo" -ldflags "-s -w" \
+    -o /out/scratchbox ./cmd/scratchbox
+
+FROM alpine:3.22
+
+RUN addgroup -S scratchbox && adduser -S -G scratchbox scratchbox
+
+WORKDIR /app
+
+COPY --from=builder /out/scratchbox /usr/local/bin/scratchbox
+COPY docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
+
+RUN chmod +x /usr/local/bin/docker-entrypoint.sh && \
+    mkdir -p /data /config && chown -R scratchbox:scratchbox /data /config
+
+USER scratchbox
+
+EXPOSE 8080
+
+VOLUME ["/data", "/config"]
+
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]