Fix error preventing calendar from displaying correctly

Add missing Button import to CalendarGrid component to resolve ReferenceError.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: a8a78c07-e900-425c-a577-5b4c5894379d
Replit-Commit-Checkpoint-Type: full_checkpoint
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client/src/components/CalendarGrid.tsx

@@ -2,6 +2,7 @@ import { format, startOfMonth, endOfMonth, eachDayOfInterval, isSameDay, isSameM
 import { fr } from "date-fns/locale";
 import { safeDate } from "@/lib/dateUtils";
 import { Plus, Check } from "lucide-react";
+import { Button } from "@/components/ui/button";
 import type { OrderWithRelations, DeliveryWithRelations } from "@shared/schema";
 
 interface CalendarGridProps {