refactor: update terminology in board view components

- Renamed "Worktrees" to "Worktree Bar" in the BoardHeader component for clarity.
- Updated comments and labels in AddFeatureDialog, PlanSettingsDialog, and WorktreeSettingsDialog to reflect the new terminology and improve user understanding of worktree mode functionality.

apps/ui/src/components/views/board-view/board-header.tsx

@@ -138,7 +138,7 @@ export function BoardHeader({
           <div className={controlContainerClass} data-testid="worktrees-toggle-container">
             <GitBranch className="w-4 h-4 text-muted-foreground" />
             <Label htmlFor="worktrees-toggle" className="text-sm font-medium cursor-pointer">
-              Worktrees
+              Worktree Bar
             </Label>
             <Switch
               id="worktrees-toggle"