[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.h

@@ -0,0 +1,43 @@
+/**
+ * @file latency_graph_widget.h
+ * @ingroup Client
+ */
+
+#ifndef LATENCY_GRAPH_WIDGET_H
+#define LATENCY_GRAPH_WIDGET_H
+
+#include <QList>
+#include <QWidget>
+
+/**
+ * @brief Bar graph of recent network round-trip samples.
+ *
+ * Draws one bar per sample, oldest on the left. Bar height is relative to the
+ * window's own scale so the shape of the variance stays readable, while bar
+ * color maps each sample onto an absolute quality ramp (green at rest through
+ * red at ColorScaleMs) so a steady good ping never looks alarming. Size
+ * agnostic: the status bar embeds a small instance while the latency detail
+ * popup shows a large one.
+ */
+class LatencyGraphWidget : public QWidget
+{
+    Q_OBJECT
+public:
+    explicit LatencyGraphWidget(QWidget *parent = nullptr);
+
+    /// Sample in milliseconds that maps to a fully red bar.
+    static constexpr qint64 ColorScaleMs = 500;
+
+    void setSamples(const QList<int> &samplesMs);
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+
+private:
+    /// Floor of the vertical scale in milliseconds. Keeps small windows readable.
+    static constexpr qint64 MinScaleMs = 100;
+
+    QList<int> samples;
+};
+
+#endif