feat : composant MalioDate (datepicker) avec calendrier, vue mois, bornes et effacement (#MUI-33)

Sous-composants internes (CalendarHeader, MonthGrid, MonthPicker), composant
public Date.vue, tests d'intégration, story Histoire et page playground.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.playground/pages/composant/date/date.vue

@@ -0,0 +1,53 @@
+<template>
+  <div class="max-w-md space-y-6">
+    <h1 class="text-2xl font-bold">MalioDate</h1>
+
+    <MalioDate
+      v-model="value"
+      label="Date de naissance"
+      hint="Clique pour ouvrir le calendrier"
+    />
+
+    <div class="rounded border p-3 text-sm">
+      <p>Valeur (ISO) : <code>{{ value ?? 'null' }}</code></p>
+    </div>
+
+    <div class="flex gap-2">
+      <button
+        type="button"
+        class="rounded bg-m-primary px-3 py-1.5 text-white"
+        @click="value = '2026-12-25'"
+      >
+        Forcer le 25/12/2026
+      </button>
+      <button
+        type="button"
+        class="rounded border px-3 py-1.5"
+        @click="value = null"
+      >
+        Réinitialiser
+      </button>
+    </div>
+
+    <MalioDate
+      v-model="bounded"
+      label="Date bornée"
+      :min="todayIso"
+      :max="maxIso"
+      hint="Entre aujourd'hui et +30 jours"
+    />
+  </div>
+</template>
+
+<script setup lang="ts">
+import {ref} from 'vue'
+
+const pad = (n: number) => String(n).padStart(2, '0')
+const toIso = (d: Date) => `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`
+const now = new Date()
+const todayIso = toIso(now)
+const maxIso = toIso(new Date(now.getTime() + 30 * 86400000))
+
+const value = ref<string | null>(null)
+const bounded = ref<string | null>(null)
+</script>