feat: add PlanningDurationService for estimating planning duration

- Implemented PlanningDurationService to provide an indicative wait time before calculation based on user input and calendar settings.
- Introduced duration estimation logic that considers horizon dates, balances, and rules without triggering a calculation.
- Enhanced user input component to display estimated duration using the new service.
- Updated translation files to include new duration estimate strings in multiple languages.
- Added tests for PlanningDurationService to ensure accurate duration estimation and calibration.
- Refactored leave planner service to remove hardcoded deadlines and improve worker responsiveness.

src/app/components/user-input/user-input.ts

@@ -9,6 +9,7 @@ import { MatButtonModule } from '@angular/material/button';
 import { VacDay } from '../../services/calendar-service';
 import { TranslationService } from '../../services/translation-service';
 import { CalendarSettingsService } from '../../services/calendar-settings-service';
+import { PlanningDurationService } from '../../services/planning-duration.service';
 
 @Component({
 	selector: 'app-user-input',
@@ -28,7 +29,18 @@ import { CalendarSettingsService } from '../../services/calendar-settings-servic
 export class UserInput {
 	private userInputService: UserInputService = inject(UserInputService);
 	protected readonly calendarSettings = inject(CalendarSettingsService);
+	protected readonly duration = inject(PlanningDurationService);
 	protected readonly translationService = inject(TranslationService);
+	protected readonly durationLabel = computed(() => {
+		const estimate = this.duration.estimate();
+		if (!estimate) return '';
+		return this.tr()
+			.userInput.durationEstimate.replace(
+				'{range}',
+				`${estimate.minimum}–${estimate.maximum}`,
+			)
+			.replace('{unit}', this.tr().userInput.durationUnits[estimate.unit]);
+	});
 
 	get tr() {
 		return this.translationService.tr;