refactor(server): merge authserver implementation

server/Dockerfile.backend

@@ -0,0 +1,26 @@
+FROM golang:1.26-alpine AS builder
+
+WORKDIR /app
+
+ENV GOPROXY=https://goproxy.cn,direct \
+    GOSUMDB=sum.golang.google.cn
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY cmd ./cmd
+COPY internal ./internal
+
+RUN CGO_ENABLED=0 GOOS=linux go build -o /out/authserver ./cmd/server
+
+FROM alpine:3.22
+
+RUN apk add --no-cache ca-certificates tzdata
+
+WORKDIR /authserver/backend
+
+COPY --from=builder /out/authserver /usr/local/bin/authserver
+
+EXPOSE 8083
+
+CMD ["authserver"]