feat(VDatePicker): add readonly prop

[Haviles04]

Description

fixes #22282

<template>
  <v-app>
    <v-container>
      <strong>Read Only?</strong>
      <v-date-picker
        :show-adjacent-months="true"
        aria-readonly="true"
        class="pa-"
        elevation="0"
        multiple="range"
        hide-header
        hide-title
        readonly
      />
      <br>
      <strong>Disabled</strong>
      <v-date-picker
        :model-value="['2025-11-29', '2025-11-30', '2025-12-1']"
        :show-adjacent-months="true"
        aria-readonly="true"
        class="pa-"
        elevation="0"
        multiple="range"
        disabled
        hide-header
        hide-title
      />
    </v-container>
  </v-app>
</template>

<script setup>

</script>

[J-Sek]

Should probably target dev branch