feat: add Docker deployment support

- Multi-stage Dockerfile (Node build + Go build + Alpine runtime)
- docker-compose.yml with named volume for data persistence
- In-container Nginx reverse proxy (static files + API)
- Entrypoint script for graceful process management
- .dockerignore for optimized build context
- Updated README (zh/en) with Docker quick start and deployment docs

Closes #14

Dockerfile

@@ -0,0 +1,62 @@
+# ---- Stage 1: Build frontend ----
+FROM node:20-alpine AS web-builder
+
+WORKDIR /build/web
+COPY web/package.json web/package-lock.json ./
+RUN npm ci
+COPY web/ ./
+RUN npm run build
+
+
+# ---- Stage 2: Build backend ----
+FROM golang:1.25-alpine AS server-builder
+
+WORKDIR /build/server
+COPY server/go.mod server/go.sum ./
+RUN go mod download
+COPY server/ ./
+RUN go build -trimpath -ldflags="-s -w" -o backupx ./cmd/backupx
+
+
+# ---- Stage 3: Production image ----
+FROM alpine:3.21
+
+RUN apk add --no-cache \
+    nginx \
+    tzdata \
+    ca-certificates \
+    # Required by mysql/postgresql backup tasks
+    mysql-client \
+    postgresql16-client \
+    && rm -rf /var/cache/apk/*
+
+# Create app user
+RUN addgroup -S backupx && adduser -S -G backupx -h /app backupx
+
+# Copy backend binary
+COPY --from=server-builder /build/server/backupx /app/bin/backupx
+
+# Copy frontend static files
+COPY --from=web-builder /build/web/dist /app/web
+
+# Copy nginx config
+COPY deploy/docker/nginx.conf /etc/nginx/http.d/default.conf
+
+# Copy entrypoint
+COPY deploy/docker/entrypoint.sh /app/entrypoint.sh
+RUN chmod +x /app/entrypoint.sh
+
+# Create data directories
+RUN mkdir -p /app/data /tmp/backupx && \
+    chown -R backupx:backupx /app /tmp/backupx
+
+# Nginx needs to write to these dirs
+RUN mkdir -p /var/lib/nginx/tmp /var/log/nginx && \
+    chown -R backupx:backupx /var/lib/nginx /var/log/nginx /run/nginx
+
+WORKDIR /app
+EXPOSE 8340
+
+VOLUME ["/app/data"]
+
+ENTRYPOINT ["/app/entrypoint.sh"]