Show remaining budget in mobile category buttons

Each category button now displays "X € restants" below the name,
alongside the existing progress gauge and percentage — so the user
sees both how much of the budget is used and how much is left
without leaving the entry form. Remaining is floored at 0 to match
the gauge's 100% cap.

categoryProgress now returns a ['pct', 'remaining'] pair per category
instead of a bare percentage; tests updated accordingly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/Livewire/Suivi/Index.php

@@ -199,7 +199,10 @@ class Index extends Component
 
                 $tracked = $this->trackedForCategoryThisMonth($category, $year, $month);
 
-                return [$category->id => min(100, round($tracked / $budget * 100))];
+                return [$category->id => [
+                    'pct' => min(100, round($tracked / $budget * 100)),
+                    'remaining' => max(0, $budget - $tracked),
+                ]];
             });
 
         return view('livewire.suivi.index', [