fix(miniapp): keep date-only values stable across timezones

apps/miniapp/src/lib/dates.ts

@@ -4,13 +4,54 @@ function localeTag(locale: Locale): string {
   return locale === 'ru' ? 'ru-RU' : 'en-US'
 }
 
+function formatCalendarDate(
+  year: number,
+  month: number,
+  day: number,
+  locale: Locale
+): string | null {
+  if (
+    !Number.isInteger(year) ||
+    !Number.isInteger(month) ||
+    !Number.isInteger(day) ||
+    month < 1 ||
+    month > 12 ||
+    day < 1 ||
+    day > 31
+  ) {
+    return null
+  }
+
+  const includeYear = year !== new Date().getUTCFullYear()
+
+  return new Intl.DateTimeFormat(localeTag(locale), {
+    month: 'long',
+    day: 'numeric',
+    ...(includeYear ? { year: 'numeric' } : {}),
+    timeZone: 'UTC'
+  }).format(new Date(Date.UTC(year, month - 1, day)))
+}
+
 export function formatFriendlyDate(value: string, locale: Locale): string {
+  const calendarDateMatch = /^(\d{4})-(\d{2})-(\d{2})$/.exec(value)
+  if (calendarDateMatch) {
+    const formatted = formatCalendarDate(
+      Number.parseInt(calendarDateMatch[1] ?? '', 10),
+      Number.parseInt(calendarDateMatch[2] ?? '', 10),
+      Number.parseInt(calendarDateMatch[3] ?? '', 10),
+      locale
+    )
+    if (formatted) {
+      return formatted
+    }
+  }
+
   const date = new Date(value)
   if (Number.isNaN(date.getTime())) {
     return value
   }
 
-  const includeYear = date.getUTCFullYear() !== new Date().getUTCFullYear()
+  const includeYear = date.getFullYear() !== new Date().getFullYear()
 
   return new Intl.DateTimeFormat(localeTag(locale), {
     month: 'long',