Improves date header localization

Adds locale support to the date header renderer and date service.

This change ensures that the day names are displayed correctly based on the user's configured locale.

The date header now uses the configured locale to display the day name in the correct language.
The day name is now displayed in uppercase.

Additionally, styles the date header to highlight today's date.

src/core/CalendarConfig.ts

@@ -546,6 +546,13 @@ export class CalendarConfig {
     return this.timeFormatConfig.timezone;
   }
 
+  /**
+   * Get configured locale
+   */
+  getLocale(): string {
+    return this.timeFormatConfig.locale;
+  }
+
   /**
    * Check if using 24-hour format
    */

src/renderers/HeaderRenderer.ts

@@ -34,8 +34,9 @@ export class DateHeaderRenderer implements HeaderRenderer {
     const allDayContainer = document.createElement('swp-allday-container');
     calendarHeader.appendChild(allDayContainer);
 
-    // Initialize date service with config
+    // Initialize date service with timezone and locale from config
     const timezone = config.getTimezone?.() || 'Europe/Copenhagen';
+    const locale = config.getLocale?.() || 'da-DK';
     this.dateService = new DateService(timezone);
 
     const workWeekSettings = config.getWorkWeekSettings();
@@ -49,7 +50,7 @@ export class DateHeaderRenderer implements HeaderRenderer {
         (header as any).dataset.today = 'true';
       }
 
-      const dayName = this.dateService.getDayName(date, 'short');
+      const dayName = this.dateService.getDayName(date, 'long', locale).toUpperCase();
 
       header.innerHTML = `
         <swp-day-name>${dayName}</swp-day-name>

src/utils/DateService.ts

@@ -139,10 +139,11 @@ export class DateService {
    * Get day name for a date
    * @param date - Date to get day name for
    * @param format - 'short' (e.g., 'Mon') or 'long' (e.g., 'Monday')
+   * @param locale - Locale for day name (default: 'da-DK')
    * @returns Day name
    */
-  public getDayName(date: Date, format: 'short' | 'long' = 'short'): string {
-    const formatter = new Intl.DateTimeFormat('en-US', {
+  public getDayName(date: Date, format: 'short' | 'long' = 'short', locale: string = 'da-DK'): string {
+    const formatter = new Intl.DateTimeFormat(locale, {
       weekday: format
     });
     return formatter.format(date);

wwwroot/css/calendar-layout-css.css

@@ -246,7 +246,7 @@ swp-day-header {
   flex-direction: column;
   align-items: center;
   justify-content: center;
-  padding-top: 7px;
+  padding-top: 3px;
 }
 
 swp-day-header:last-child {
@@ -299,27 +299,27 @@ swp-day-name {
   font-weight: 500;
   font-size: 12px;
   color: var(--color-text-secondary);
+  letter-spacing: 0.1em;
 }
 
 swp-day-date {
   display: block;
-  font-size: 20px;
-  font-weight: 600;
+  font-size: 30px;
   margin-top: 4px;
-  height: 41px;
+}
 
+/* Highlight entire header for today */
+swp-day-header[data-today="true"] {
+  background: rgba(33, 150, 243, 0.1);
+}
+
+swp-day-header[data-today="true"] swp-day-name {
+  color: var(--color-primary);
+  font-weight: 600;
 }
 
 swp-day-header[data-today="true"] swp-day-date {
   color: var(--color-primary);
-  background: rgba(33, 150, 243, 0.1);
-  border-radius: 50%;
-  width: 41px;
-  height: 41px;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  margin: 4px auto 0;
 }
 
 /* Ghost columns for mouseenter events */