feat: add caching for backend objects

app/composables/useBookingDraft.ts

@@ -0,0 +1,26 @@
+import type { Database } from '~/types/supabase'
+
+type Boat = Database['public']['Tables']['boats']['Row']
+
+export interface BookingDraft {
+  boat: Boat
+  startTime: string
+  endTime: string
+}
+
+const _draft = ref<BookingDraft | null>(null)
+
+export function useBookingDraft() {
+  function set(boat: Boat, startTime: string, endTime: string): void {
+    _draft.value = { boat, startTime, endTime }
+  }
+
+  /** Reads and clears the draft — call once in the destination page. */
+  function take(): BookingDraft | null {
+    const val = _draft.value
+    _draft.value = null
+    return val
+  }
+
+  return { set, take }
+}