feat(server): Go 模块骨架 + 工具链 [tsk_L2k2VrEujof8]

新建 server/ Go 模块：
- go.mod: module github.com/wangjia/pangolin/server, Go 1.22
  依赖: go-chi/chi/v5, google/uuid
- tools.go: //go:build tools 锁定 oapi-codegen / golang-migrate 版本
- cmd/server/main.go: chi router + GET /healthz → {"status":"ok"}，监听 :8080
- cmd/migrate/main.go: 占位入口（实逻辑归 1e）
- internal/{config,store,apierr,idgen,auth,codes,devices,nodes,usage,admin}/doc.go
  各包职责说明
- Makefile: build/test/vet/lint/generate/migrate-up/migrate-down
- .golangci.yml: govet/errcheck/staticcheck/revive/gofmt 基线
- README.md: 定位 + 目录树 + make 入口说明
- setup.sh: 首次 go mod tidy 引导脚本（go.sum 需运行后生成）

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/cmd/server/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"log"
+	"net/http"
+	"os"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
+)
+
+func main() {
+	addr := flag.String("addr", "", "listen address (default :8080, overridden by ADDR env)")
+	flag.Parse()
+
+	if *addr == "" {
+		if v := os.Getenv("ADDR"); v != "" {
+			*addr = v
+		} else {
+			*addr = ":8080"
+		}
+	}
+
+	r := chi.NewRouter()
+	r.Use(middleware.Logger)
+	r.Use(middleware.Recoverer)
+
+	r.Get("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusOK)
+		_ = json.NewEncoder(w).Encode(map[string]string{"status": "ok"})
+	})
+
+	log.Printf("pangolin server listening on %s", *addr)
+	if err := http.ListenAndServe(*addr, r); err != nil {
+		log.Fatalf("server error: %v", err)
+	}
+}