feat(scheduled-tasks): add cron syntax support to task editor dialog (#1593)

Adds a 'Cron' schedule type option to the scheduled task editor, allowing
users to create and edit cron-based schedules through the UI.

- Add cron expression input with inline validation (cron-parser)
- Show next 4 upcoming run times as a preview
- Provide clickable example chips (every 5min, hourly, Monday 9am, etc.)
- Preserve cron expressions when editing existing cron tasks
- Add cron.ts utility module for validation and next-run computation
- Add i18n keys across all 8 locale files

Closes #1586

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/lib/i18n/messages/uk.ts

@@ -214,6 +214,7 @@ export const dict: Record<I18nKey, string> = {
   "sessions.scheduledTasks.editor.scheduleType.daily": "Щодня",
   "sessions.scheduledTasks.editor.scheduleType.weekly": "Щотижня",
   "sessions.scheduledTasks.editor.scheduleType.once": "Одноразовий",
+  "sessions.scheduledTasks.editor.scheduleType.cron": "Cron",
   "sessions.scheduledTasks.editor.date.label": "Дата",
   "sessions.scheduledTasks.editor.date.placeholder": "Вибрати дату",
   "sessions.scheduledTasks.editor.date.previousMonth": "Попередній місяць",
@@ -252,6 +253,17 @@ export const dict: Record<I18nKey, string> = {
   "sessions.scheduledTasks.editor.validation.atLeastOneTime": "Додайте принаймні один дійсний час",
   "sessions.scheduledTasks.editor.validation.atLeastOneWeekday": "Виберіть хоча б один день тижня",
   "sessions.scheduledTasks.editor.validation.timezoneRequired": "Потрібно вказати часовий пояс",
+  "sessions.scheduledTasks.editor.validation.cronRequired": "Потрібно вказати cron-вираз",
+  "sessions.scheduledTasks.editor.validation.cronInvalid": "Недійсний cron-вираз",
+  "sessions.scheduledTasks.editor.cronExpression.label": "Cron-вираз",
+  "sessions.scheduledTasks.editor.cronExpression.placeholder": "*/5 * * * *",
+  "sessions.scheduledTasks.editor.cronExpression.nextRuns": "Наступні запуски",
+  "sessions.scheduledTasks.editor.cronExpression.examples": "Приклади",
+  "sessions.scheduledTasks.editor.cronExpression.examples.every5min": "Кожні 5 хвилин",
+  "sessions.scheduledTasks.editor.cronExpression.examples.everyHour": "Щогодини",
+  "sessions.scheduledTasks.editor.cronExpression.examples.monday9am": "Щопонеділка о 9:00",
+  "sessions.scheduledTasks.editor.cronExpression.examples.9am5pm": "Щодня о 9:00 і 17:00",
+  "sessions.scheduledTasks.editor.cronExpression.examples.firstOfMonth": "Першого числа кожного місяця",
   "multirun.launcher.title": "Новий Multi-Run",
   "multirun.launcher.actions.closeEsc": "Закрити (Esc)",
   "multirun.launcher.actions.cancel": "Скасувати",