feat(planning): #62 #63 #64 enhance leave planner with calculation date and entitlement details

- Introduced calculationDate in various service interfaces and snapshots to track the date of planning calculations.
- Added futureEntitlement and includedEntitlement fields to the translation service and respective language files for better user feedback.
- Updated leave-planner.worker to handle calculationDate and declaredDays in requests.
- Enhanced tests to ensure proper handling of calculation dates and artifact retention during planning processes.
- Improved snapshot and explanation outputs to include calculation date for clarity in planning results.

src/app/services/translation-service.ts

@@ -128,6 +128,9 @@ export interface AppTranslations {
 		};
 	};
 	planning: {
+		calculationDate: string;
+		futureEntitlement: string;
+		includedEntitlement: string;
 		comparison: {
 			title: string;
 			candidate: string;