refactor : migrate UI to Malio layer-ui components (MalioButton, MalioDrawer, MalioSelectCheckbox)

- Replace all AppDrawer with MalioDrawer across 10 drawer components
- Replace native <button> with MalioButton/MalioButtonIcon in all pages and components
- Fix TimeTrackingExportDrawer: use MalioSelectCheckbox for multi-select filters
- Add Malio design system colors (m-btn-*, m-disabled, m-surface) to tailwind.config.ts
- Align toggle button heights with MalioButton (h-[40px])

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/components/admin/AdminClientTab.vue

@@ -2,12 +2,13 @@
     <div>
         <div class="flex items-center justify-between">
             <h2 class="text-lg font-bold text-neutral-900">Clients</h2>
-            <button
-                class="rounded-md bg-primary-500 px-4 py-2 text-sm font-semibold text-white hover:bg-secondary-500"
+            <MalioButton
+                icon-name="mdi:plus"
+                icon-position="left"
+                button-class="w-auto px-4"
+                label="Ajouter un client"
                 @click="openCreate"
-            >
-                + Ajouter un client
-            </button>
+            />
         </div>
 
         <DataTable