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/.golangci.yml

@@ -0,0 +1,22 @@
+version: "2"
+
+linters:
+  enable:
+    - govet
+    - errcheck
+    - staticcheck
+    - revive
+    - gofmt
+
+linters-settings:
+  revive:
+    rules:
+      - name: exported
+      - name: var-naming
+
+issues:
+  exclude-rules:
+    # tools.go is build-tag-only, ignore unused import warnings
+    - path: tools\.go
+      linters:
+        - revive