✨ feat(matrix-bots): add i18n system and direct message fallback

- Add I18nService with per-user language preferences (de/en)
- Add !language/!sprache command to all 4 bots (todo, calendar, contacts, clock)
- Add fallback behavior: messages without commands create tasks/events/contacts/timers
- Improve clock bot duration parsing to accept bare numbers as minutes (e.g. "25" = 25min)
- Add support for more duration formats: "25 minuten", "1 stunde", etc.

Language preferences stored in SessionService, default configurable via BOT_DEFAULT_LANGUAGE env var.

services/matrix-calendar-bot/src/bot/bot.module.ts

@@ -7,6 +7,7 @@ import {
 	SessionModule,
 	CreditModule,
 	CalendarApiService,
+	I18nModule,
 } from '@manacore/bot-services';
 
 // Factory provider for CalendarApiService
@@ -28,6 +29,7 @@ const calendarApiServiceProvider = {
 		}),
 		SessionModule.forRoot({ storageMode: 'redis' }),
 		CreditModule.forRoot(),
+		I18nModule.forRoot(),
 	],
 	providers: [MatrixService, calendarApiServiceProvider],
 	exports: [MatrixService],