[Client] Alt badges, breadcrumb trail, investigate button (#7516)

* [Client] Alt badges, breadcrumb trail, investigate button

AltTableDelegate paints palette-tinted match badges with paint-through selection, style warning/critical icons on nonzero counts, and font/elision handling. TabAlts gains a clickable breadcrumb trail, an Investigate-this-user button, and bold usernames. Async alts responses are guarded against stale investigations.

* [Client] Fix alt badge and trail review findings

- Drop the dead VPN warning branch: rowVisible() already hides IP rows
  above the threshold, so setVpnThreshold(), its member and the spin-box
  connect never took effect.
- Dim IP rows at shared_count > 2 instead of > 1: the count already
  includes the investigated account, so every IP row was dimmed.
- Truncate backStack when a breadcrumb is clicked instead of pushing the
  current user again, so the trail keeps a single path and Back works.
- Word-wrap the trail label so a long chain cannot widen the tab.
- Extract the status/match pill painting into widgets/utility/pill_painter
  and use it from both delegates instead of duplicating it.

* [Client] Route investigate() through the trail helper

---------

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

cockatrice/src/interface/widgets/utility/pill_painter.h

@@ -0,0 +1,29 @@
+#ifndef PILL_PAINTER_H
+#define PILL_PAINTER_H
+
+#include <QPalette>
+#include <QString>
+
+class QPainter;
+class QStyleOptionViewItem;
+
+namespace pill_painter
+{
+constexpr int PAD_X = 10;
+constexpr int PAD_Y = 4;
+
+/**
+ * Draws a translucent, palette-tinted rounded pill inside the option's rect and
+ * paints the text elided and centred on it, so badges follow the active theme.
+ * Returns false when the cell is too small to hold a pill, leaving the caller to
+ * fall back to default painting.
+ */
+bool paint(QPainter *painter,
+           const QStyleOptionViewItem &option,
+           QPalette::ColorRole tintRole,
+           QPalette::ColorRole textRole,
+           const QString &text);
+
+} // namespace pill_painter
+
+#endif // PILL_PAINTER_H