[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.

cockatrice/src/interface/widgets/tabs/alt_table_delegate.h

@@ -6,10 +6,10 @@
 
 /**
  * Badge + icon painting for the User Alts table. The match-evidence column
- * renders as a palette-tinted pill per match type (email / client id / IP),
- * with the style's warning icon once an IP is shared by more than the VPN
- * threshold. Warn/ban counts gain the style's warning/critical icons when
- * nonzero. Selected rows and unknown content fall back to default painting.
+ * renders as a palette-tinted pill per match type (email / client id / IP), and
+ * an IP shared by more than one other account is dimmed. Warn/ban counts gain
+ * the style's warning/critical icons when nonzero. Selected rows and unknown
+ * content fall back to default painting.
  */
 class AltTableDelegate : public QStyledItemDelegate
 {
@@ -20,7 +20,6 @@ public:
                               int bansColumn,
                               int sharedColumn,
                               QObject *parent = nullptr);
-    void setVpnThreshold(int threshold);
     void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
     [[nodiscard]] QSize sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const override;
 
@@ -29,7 +28,6 @@ private:
     int warnsColumn;
     int bansColumn;
     int sharedColumn;
-    int vpnThreshold = 10;
 };
 
 #endif // ALT_TABLE_DELEGATE_H