build: 分离开发与发布环境的 Docker 构建配置

- 新增 Dockerfile.release 用于生产环境，仅包含运行所需的最小依赖
- 重构原 Dockerfile 为多阶段构建，集成前端构建与后端编译
- 更新 .goreleaser.yaml 以使用新的发布镜像配置
- 新增 GitHub Actions 工作流用于自动构建和推送 Docker 镜像

Dockerfile

@@ -1,16 +1,64 @@
-FROM debian:latest
+# Stage 1: Build Frontend
+FROM node:20-alpine AS frontend-builder
+
+WORKDIR /web
+
+# Copy package files first for caching
+COPY web/package*.json ./
+COPY web/tsconfig*.json ./
+COPY web/vite.config.ts ./
+COPY web/index.html ./
+
+# Install dependencies
+RUN npm install
+
+# Copy source code
+COPY web/ ./
+
+# Build frontend
+RUN npm run build
+
+# Stage 2: Build Backend
+FROM golang:1.24 AS backend-builder
+
+WORKDIR /app
+
+# Copy Go module files
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Copy frontend build artifacts to the location expected by go:embed
+# The embed directive in main.go is //go:embed web/dist/*
+COPY --from=frontend-builder /web/dist ./web/dist
+
+# Build the binary
+# CGO_ENABLED=0 for static binary
+RUN CGO_ENABLED=0 GOOS=linux go build -o Message-Nest main.go
+
+# Stage 3: Runtime
+FROM debian:stable-slim
 
 ENV TZ=Asia/Shanghai
 
-RUN apt update \
-        && apt install -y ca-certificates \
-        && update-ca-certificates \
-        && rm -rf /var/lib/apt/lists/*
-
-COPY ./ /app/
+RUN apt-get update \
+    && apt-get install -y ca-certificates tzdata \
+    && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
+
+# Copy binary
+COPY --from=backend-builder /app/Message-Nest .
+
+# Copy configuration directory (contains app.example.ini)
+COPY --from=backend-builder /app/conf ./conf
+
+# Copy other necessary files
+COPY --from=backend-builder /app/LICENSE .
+COPY --from=backend-builder /app/README.md .
+
 EXPOSE 8000
 
-CMD ["/app/Message-Nest"]
-
+CMD ["./Message-Nest"]