fix: tasks on timeline not adjusting to zoom

There are issues in svelte with cascading dependencies
in reactive declarations, from what I understand.
Since `background color` relies on `$store.timelineColored`,
having `textColor` rely on both seemed to cause issues.
Removing the direct dependency of the store works,
anyway.

src/ui/components/task.svelte

@@ -44,7 +44,7 @@
     : "var(--background-primary)";
 
   let properContrastColors: IContrastColors;
-  $: properContrastColors = $settings.timelineColored && planItem.startTime
+  $: properContrastColors = backgroundColor.startsWith("#") && planItem.startTime
     ? getTextColorWithEnoughContrast(backgroundColor)
     : {
       normal: "var(--text-normal)",