feat(carbet): add lastBookedAt and endpoint

prisma/migrations/20260530173000_add_last_booked_at/migration.sql

@@ -0,0 +1,2 @@
+ALTER TABLE "Carbet"
+ADD COLUMN "lastBookedAt" TIMESTAMP(3);

prisma/schema.prisma

@@ -109,6 +109,7 @@ model Carbet {
   pirogueDurationMin Int
   capacity           Int
   status             CarbetStatus @default(DRAFT)
+  lastBookedAt       DateTime?
   createdAt          DateTime     @default(now())
   updatedAt          DateTime     @updatedAt