minor improvements:

- page titles
- favicon
- background logo

frontend/src/routes/task/Index.svelte

@@ -96,6 +96,10 @@
     onMount(load);
 </script>
 
+<svelte:head>
+    <title>Umbrella – {t('tasks')}</title>
+</svelte:head>
+
 <fieldset>
     <legend>{loading ? t('loading_object',{object:t('task_list')}) : t('task_list')}</legend>
     {#if error}