Improved calendar day styling. Large numbers, now today marker and other tweaks.

src/utils/date.js

@@ -192,6 +192,17 @@ function formatTodayString(date) {
   return formatted.charAt(0).toUpperCase() + formatted.slice(1)
 }
 
+/**
+ * Format date as compact string for day cell corner (e.g., "Mon 15 Jan")
+ */
+function formatDateCompact(date) {
+  return date.toLocaleDateString(undefined, { 
+    weekday: 'short', 
+    day: 'numeric', 
+    month: 'short' 
+  }).replace(", ", " ")
+}
+
 export {
   // constants
   monthAbbr,
@@ -218,6 +229,7 @@ export {
   formatDateRange,
   formatDateShort,
   formatDateLong,
+  formatDateCompact,
   formatTodayString,
   lunarPhaseSymbol,
   // iso helpers re-export