qt: Add formatBytesps function for bytes per second display

Add a new GUI utility function to format bytes per second values with appropriate
units (B/s, kB/s, MB/s, GB/s) and precision, ensuring consistent and readable
display of network traffic rates in the traffic graph widget.

Author: rebroad

src/qt/guiutil.cpp

@@ -833,6 +833,40 @@ QString formatBytes(uint64_t bytes)
     return QObject::tr("%1 GB").arg(bytes / 1'000'000'000);
 }
 
+QString formatBytesps(float val)
+{
+    if (val < 10)
+        //: "Bytes per second"
+        return QObject::tr("%1 B/s").arg(0.01 * int(val * 100 + 0.5));
+    if (val < 100)
+        //: "Bytes per second"
+        return QObject::tr("%1 B/s").arg(0.1 * int(val * 10 + 0.5));
+    if (val < 1'000)
+        //: "Bytes per second"
+        return QObject::tr("%1 B/s").arg(int(val + 0.5));
+    if (val < 10'000)
+        //: "Kilobytes per second"
+        return QObject::tr("%1 kB/s").arg(0.01 * int(val / 10 + 0.5));
+    if (val < 100'000)
+        //: "Kilobytes per second"
+        return QObject::tr("%1 kB/s").arg(0.1 * int(val / 100 + 0.5));
+    if (val < 1'000'000)
+        //: "Kilobytes per second"
+        return QObject::tr("%1 kB/s").arg(int(val / 1'000 + 0.5));
+    if (val < 10'000'000)
+        //: "Megabytes per second"
+        return QObject::tr("%1 MB/s").arg(0.01 * int(val / 10'000 + 0.5));
+    if (val < 100'000'000)
+        //: "Megabytes per second"
+        return QObject::tr("%1 MB/s").arg(0.1 * int(val / 100'000 + 0.5));
+    if (val < 10'000'000'000)
+        //: "Megabytes per second"
+        return QObject::tr("%1 MB/s").arg(long(val / 1'000'000 + 0.5));
+
+    //: "Gigabytes per second"
+    return QObject::tr("%1 GB/s").arg(long(val / 1'000'000'000 + 0.5));
+}
+
 qreal calculateIdealFontSize(int width, const QString& text, QFont font, qreal minPointSize, qreal font_size) {
     while(font_size >= minPointSize) {
         font.setPointSizeF(font_size);

src/qt/guiutil.h

@@ -246,6 +246,7 @@ namespace GUIUtil
     QString formatNiceTimeOffset(qint64 secs);
 
     QString formatBytes(uint64_t bytes);
+    QString formatBytesps(float bytes);
 
     qreal calculateIdealFontSize(int width, const QString& text, QFont font, qreal minPointSize = 4, qreal startPointSize = 14);