[Client] Show latency in status bar and server tab indicator (#7154)

* [Client] Show live connection latency in the status bar

Add a permanent status-bar label fed by ConnectionController's
pingStatsUpdated: shows the latest round-trip time, hides while
disconnected or without samples, and carries a tooltip with
Last/Median/95th percentile/Maximum over the rolling sample window
(mirrored into the accessible description). The server tab gets the
same stats as its tooltip.

Took 2 minutes

Took 2 minutes

Took 1 minute

Took 48 seconds

Took 25 seconds

Took 4 minutes

* [Client] Graph connection latency history in the status bar

Add LatencyGraphWidget, a size-agnostic bar sparkline over the rolling
sample window: heights scale to the window's own range while colors map
onto an absolute quality ramp, so a steady good ping stays green. Embed
it in the new LatencyStatusWidget together with the textual ping
readout and feed both through ConnectionController's forwarded signals;
the whole area hides while disconnected or without samples.

Took 9 minutes

Took 14 seconds

* [Client] Show latency details when clicking the ping display

Clicking the status bar ping area opens a popup with a larger instance
of the latency graph plus the numeric statistics, selectable and
mirrored into the accessible name. Qt::Popup closes it on any outside
click; contents refresh live while open.


Took 33 seconds

* Fixup from core commit

Took 6 minutes

Took 5 seconds

Took 5 minutes

* Lint.

Took 12 minutes

* Consolidate.

Took 6 minutes

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>

cockatrice/src/client/latency_graph_widget.cpp

@@ -0,0 +1,51 @@
+/**
+ * @file latency_graph_widget.cpp
+ * @ingroup Client
+ */
+
+#include "latency_graph_widget.h"
+
+#include <QPainter>
+
+LatencyGraphWidget::LatencyGraphWidget(QWidget *parent) : QWidget(parent)
+{
+}
+
+void LatencyGraphWidget::setSamples(const QList<int> &samplesMs)
+{
+    samples = samplesMs;
+    update();
+}
+
+void LatencyGraphWidget::paintEvent(QPaintEvent * /* event */)
+{
+    if (samples.isEmpty()) {
+        return;
+    }
+
+    QPainter painter(this);
+
+    // Heights are relative to the window's own worst sample (floored at
+    // MinScaleMs) so the shape of the variance stays readable even when every
+    // value is small.
+    qint64 heightScaleMs = MinScaleMs;
+    for (int sample : samples) {
+        heightScaleMs = qMax(heightScaleMs, static_cast<qint64>(sample));
+    }
+
+    const qreal widthPerBar = static_cast<qreal>(width()) / samples.size();
+    for (int i = 0; i < samples.size(); ++i) {
+        const qreal heightRatio = qBound(0.0, static_cast<double>(samples.at(i)) / heightScaleMs, 1.0);
+        const qreal barHeight = heightRatio * height();
+
+        // Colors follow an absolute quality ramp: a steady good ping stays
+        // green no matter how uniform the window is.
+        const qreal colorRatio = qBound(0.0, static_cast<double>(samples.at(i)) / ColorScaleMs, 1.0);
+        QColor color;
+        color.setHsv(qRound(120.0 * (1.0 - colorRatio)), 255, 255);
+
+        const QRectF bar(static_cast<qreal>(i) * widthPerBar + 1.0, static_cast<qreal>(height()) - barHeight,
+                         qMax(1.0, widthPerBar - 2.0), barHeight);
+        painter.fillRect(bar, color);
+    }
+}