fix: resolve all go-review issues (CRITICAL/HIGH/MEDIUM)

[nagayon-935]

CRITICAL:

• portchecker: handle SetDeadline/Write errors in checkUDP to prevent goroutine leak
• traceroute: check SetControlMessage error on IPv6 send socket (non-fatal)

HIGH:

• mping: protect portChecker with pMu mutex to eliminate data race across goroutines
• mping: create real doneCh when cfg.count > 0 so TUI shows "Finished" footer
• mping: use errors.Is for pflag.ErrHelp comparison
• ui: replace 16-parameter Run() with RunOptions struct
• mping/traceroute: wrap errors with context in socket open paths and getInterfaceIP

MEDIUM:

• pinger: replace raw sync/atomic usage with atomic.Uint32 for traceCounter
• pinger/portchecker: use errors.As instead of direct type assertions for net.Error
• tui_helpers: return false (not silent zero) on ParseFloat error in filter
• tui_helpers: appendErrorLog uses incremental fmt.Fprintf (O(1)) instead of O(n) join on every call
• pinger: add godoc to NewPinger, NewPingerWithOptions, Reply