Added export/import features

src/App.svelte

@@ -46,7 +46,7 @@
          a day in progress. -->
     <div class="update">
       <span>Mise à jour disponible</span>
-      <button type="button" onclick={applyUpdate}>Installer</button>
+      <button type="button" disabled={dayState.importing} onclick={applyUpdate}>Installer</button>
     </div>
   {/if}
 
@@ -62,18 +62,21 @@
     <button
       type="button"
       class:sel={view === 'resume'}
+      disabled={dayState.importing}
       aria-current={view === 'resume'}
       onclick={() => go('resume')}>Récap</button
     >
     <button
       type="button"
       class:sel={view === 'today'}
+      disabled={dayState.importing}
       aria-current={view === 'today'}
       onclick={() => go('today')}>Journée</button
     >
     <button
       type="button"
       class:sel={view === 'settings'}
+      disabled={dayState.importing}
       aria-current={view === 'settings'}
       onclick={() => go('settings')}>Réglages</button
     >