fix(tasks): vertically center checkbox in project task row

The tooltip span wrapping the checkbox used the inherited line-height
(~24px), so the 18px inline-block checkbox sat on the baseline and
appeared misaligned with the task text. Making the span an inline-flex
container collapses it to the checkbox size and centers it properly.

frontend/src/components/tasks/partials/SingleTaskInProject.vue

@@ -14,6 +14,7 @@
 		>
 			<span
 				v-tooltip="!canMarkAsDone ? $t('task.readOnlyCheckbox') : ''"
+				class="is-inline-flex is-align-items-center"
 			>
 				<FancyCheckbox
 					v-model="task.done"