feat(cli): add cobra-based CLI to run WarpBox server

- Add `cmd/main.go` with a new `warpbox` root command and `run` subcommand
- Support `--addr` flag (default `:8080`) and delegate startup to `server.Run`
- Initialize Go module and dependencies (cobra, gin) via `go.mod`/`go.sum` to enable building the new CLI entrypointfeat(cli): add cobra-based CLI to run WarpBox server

- Add `cmd/main.go` with a new `warpbox` root command and `run` subcommand
- Support `--addr` flag (default `:8080`) and delegate startup to `server.Run`
- Initialize Go module and dependencies (cobra, gin) via `go.mod`/`go.sum` to enable building the new CLI entrypoint

lib/server/server.go

@@ -0,0 +1,13 @@
+package server
+
+import "github.com/gin-gonic/gin"
+
+func Run(addr string) error {
+	router := gin.Default()
+
+	router.GET("/", func(ctx *gin.Context) {
+		ctx.String(200, "ok")
+	})
+
+	return router.Run(addr)
+}