cmd/server: pprof server serves nothing (net/http/pprof not imported) and log.Fatal on port conflict kills the process

[whywaita]

Problem

main (cmd/server/cmd.go:36-40) sets up what looks like a profiling endpoint:

runtime.SetBlockProfileRate(1)
runtime.SetMutexProfileFraction(1)
go func() {
	log.Fatal(http.ListenAndServe("localhost:6060", nil))
}()

• net/http/pprof is not imported, so nothing is registered on http.DefaultServeMux — localhost:6060 only returns 404. The server is dead weight.
• log.Fatal inside the goroutine terminates the whole myshoes process if port 6060 is taken (e.g. two instances on one host).
• SetBlockProfileRate(1) / SetMutexProfileFraction(1) sample every blocking/mutex event unconditionally in production, which has measurable overhead.

Suggested fix

• Import _ "net/http/pprof" so the endpoint actually works.
• Log the listen error instead of log.Fatal.
• Gate the debug server and the profile rates behind an env var (e.g. MYSHOES_PPROF=1), or at least use saner rates.