Fix View Weekly Returns to use end date for filter (#1761)

We mistakenly used the start date of a weekly return submission line to determine if they should be included in a month, instead of the end date. This PR fixes this.

Author: StuAA78

app/presenters/return-submissions/view-return-submission.presenter.js

@@ -22,7 +22,7 @@ function go(returnSubmission, yearMonth) {
 
   const [requestedYear, requestedMonth] = _determineRequestedYearAndMonth(yearMonth)
   const requestedMonthLines = returnSubmissionLines.filter(
-    (line) => line.startDate.getFullYear() === requestedYear && line.startDate.getMonth() === requestedMonth
+    (line) => line.endDate.getFullYear() === requestedYear && line.endDate.getMonth() === requestedMonth
   )
 
   const method = returnSubmission.$method()

test/presenters/return-submissions/view-return-submission.presenter.test.js

@@ -268,12 +268,12 @@ describe('View Return Submissions presenter', () => {
         expect(headers).to.include('Week ending')
       })
 
-      it('includes the expected rows that start within the month', () => {
+      it('includes the expected rows that end within the month', () => {
         const result = ViewReturnSubmissionPresenter.go(testReturnSubmission, '2025-3')
 
         expect(result.tableData.rows.length).to.equal(4)
-        expect(result.tableData.rows[0]).to.include({ date: '12 April 2025' })
-        expect(result.tableData.rows[3]).to.include({ date: '3 May 2025' })
+        expect(result.tableData.rows[0]).to.include({ date: '5 April 2025' })
+        expect(result.tableData.rows).to.not.include({ date: '3 May 2025' })
       })
     })
   })