fix: make day label seem less noisy

fading-out the prefix numbers that are there to avoid layout drift helps with understanding what the label is saying (if there are leading zeros, make them less obvious but still take up space)

to achieve this, needed to update the timeline logic to produce an array of digits

this will only work so long as we only have 3 digits to work with but that'll be a wider layout issue anyway to add another prefix digit and.. let's hope we never get there...

site/src/lib/formatting.ts

@@ -1,11 +1,11 @@
-export const leftPadTwoDigits = (n: number) => {
+export const leftPadTwoDigits = (n: number): string[] => {
   if (n < 10) {
-    return `00${n}`;
+    return `00${n}`.split("");
   }
 
   if (n < 100) {
-    return `0${n}`;
+    return `0${n}`.split("");
   }
 
-  return `${n}`;
+  return `${n}`.split("");
 };