feat(tunnel): switch to yamux stream proxying and connection pooling

- Introduce pooled tunnel sessions (TunnelID/DataConnect) on client/server
- Proxy HTTP/HTTPS via raw HTTP over yamux streams; pipe TCP streams directly
- Move UI/stats into internal/shared; refactor CLI tunnel helpers; drop msgpack/hpack legacy

internal/shared/stats/format.go

@@ -0,0 +1,77 @@
+package stats
+
+// FormatBytes formats bytes to human readable string
+func FormatBytes(bytes int64) string {
+	const (
+		KB = 1024
+		MB = KB * 1024
+		GB = MB * 1024
+	)
+
+	switch {
+	case bytes >= GB:
+		return formatFloat(float64(bytes)/float64(GB)) + " GB"
+	case bytes >= MB:
+		return formatFloat(float64(bytes)/float64(MB)) + " MB"
+	case bytes >= KB:
+		return formatFloat(float64(bytes)/float64(KB)) + " KB"
+	default:
+		return formatInt(bytes) + " B"
+	}
+}
+
+// FormatSpeed formats speed (bytes per second) to human readable string
+func FormatSpeed(bytesPerSec int64) string {
+	if bytesPerSec == 0 {
+		return "0 B/s"
+	}
+	return FormatBytes(bytesPerSec) + "/s"
+}
+
+func formatFloat(f float64) string {
+	if f >= 100 {
+		return formatInt(int64(f))
+	} else if f >= 10 {
+		return formatOneDecimal(f)
+	}
+	return formatTwoDecimal(f)
+}
+
+func formatInt(i int64) string {
+	return intToStr(i)
+}
+
+func formatOneDecimal(f float64) string {
+	i := int64(f * 10)
+	whole := i / 10
+	frac := i % 10
+	return intToStr(whole) + "." + intToStr(frac)
+}
+
+func formatTwoDecimal(f float64) string {
+	i := int64(f * 100)
+	whole := i / 100
+	frac := i % 100
+	if frac < 10 {
+		return intToStr(whole) + ".0" + intToStr(frac)
+	}
+	return intToStr(whole) + "." + intToStr(frac)
+}
+
+func intToStr(i int64) string {
+	if i == 0 {
+		return "0"
+	}
+	if i < 0 {
+		return "-" + intToStr(-i)
+	}
+
+	var buf [20]byte
+	pos := len(buf)
+	for i > 0 {
+		pos--
+		buf[pos] = byte('0' + i%10)
+		i /= 10
+	}
+	return string(buf[pos:])
+}