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/es.ts

@@ -214,6 +214,7 @@ export const dict: Record<I18nKey, string> = {
   "sessions.scheduledTasks.editor.scheduleType.daily": "Diario",
   "sessions.scheduledTasks.editor.scheduleType.weekly": "Semanal",
   "sessions.scheduledTasks.editor.scheduleType.once": "Una vez",
+  "sessions.scheduledTasks.editor.scheduleType.cron": "Cron",
   "sessions.scheduledTasks.editor.date.label": "Fecha",
   "sessions.scheduledTasks.editor.date.placeholder": "Seleccionar fecha",
   "sessions.scheduledTasks.editor.date.previousMonth": "Mes anterior",
@@ -252,6 +253,17 @@ export const dict: Record<I18nKey, string> = {
   "sessions.scheduledTasks.editor.validation.atLeastOneTime": "Añadir al menos una hora válida",
   "sessions.scheduledTasks.editor.validation.atLeastOneWeekday": "Seleccionar al menos un día de la semana",
   "sessions.scheduledTasks.editor.validation.timezoneRequired": "Se requiere zona horaria",
+  "sessions.scheduledTasks.editor.validation.cronRequired": "Se requiere una expresión cron",
+  "sessions.scheduledTasks.editor.validation.cronInvalid": "Expresión cron no válida",
+  "sessions.scheduledTasks.editor.cronExpression.label": "Expresión cron",
+  "sessions.scheduledTasks.editor.cronExpression.placeholder": "*/5 * * * *",
+  "sessions.scheduledTasks.editor.cronExpression.nextRuns": "Próximas ejecuciones",
+  "sessions.scheduledTasks.editor.cronExpression.examples": "Ejemplos",
+  "sessions.scheduledTasks.editor.cronExpression.examples.every5min": "Cada 5 minutos",
+  "sessions.scheduledTasks.editor.cronExpression.examples.everyHour": "Cada hora",
+  "sessions.scheduledTasks.editor.cronExpression.examples.monday9am": "Cada lunes a las 9 a. m.",
+  "sessions.scheduledTasks.editor.cronExpression.examples.9am5pm": "9 a. m. y 5 p. m. todos los días",
+  "sessions.scheduledTasks.editor.cronExpression.examples.firstOfMonth": "Primero de cada mes",
   "multirun.launcher.title": "Nuevo Multi-Run",
   "multirun.launcher.actions.closeEsc": "Cerrar (Esc)",
   "multirun.launcher.actions.cancel": "Cancelar",