feat: Gregorian default calendar, Hymnal label, day header cleanup

- Default calendar type julian -> gregorian (new installs only)
- EN nav 'Sbornik' -> 'Hymnal', section title -> 'Liturgical Hymnal'
- Day header: text-sm on date lines, weekday dropped from Julian line,
  order: Julian / day-title / Gregorian

src/ui/app.ts

@@ -231,7 +231,7 @@ export class App {
     // Re-read settings fresh on each navigation
     this.settings = loadSettings();
     const lang = this.settings.language as LanguageCode;
-    const calendarType = this.settings.calendarType || 'julian';
+    const calendarType = this.settings.calendarType || 'gregorian';
 
     switch (this.currentView) {
       case 'calendar':