fix(test): explicit type witness on List.of(Object[]) for Mockito inference

javac couldn't infer List<Object[]> from List.of(row) when row is Object[];
adding the explicit type witness List.<Object[]>of(row) resolves the
ambiguous overload that caused the compilation error.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/java/com/example/app/report/ReportServiceTest.java

@@ -28,7 +28,8 @@ class ReportServiceTest {
     LocalDate monday = ReportService.parseIsoWeekToMonday("2026-W20");
     Object[] row = {Date.valueOf(monday), 120L, 9600L}; // 2h, 96.00 EUR
 
-    when(timeEntryRepository.aggregateByDay(anyLong(), any(), any())).thenReturn(List.of(row));
+    when(timeEntryRepository.aggregateByDay(anyLong(), any(), any()))
+        .thenReturn(List.<Object[]>of(row));
 
     WeeklyReport report = reportService.weeklyReport(1L, "2026-W20");
 
@@ -52,7 +53,7 @@ class ReportServiceTest {
     // budget 60 minutes, logged 90 — breached
     Object[] row = {1L, "Acme", 60, 100_00, 90L, 120_00L};
     when(timeEntryRepository.aggregateByProjectForMonth(anyLong(), anyInt(), anyInt()))
-        .thenReturn(List.of(row));
+        .thenReturn(List.<Object[]>of(row));
 
     var report = reportService.monthlyReport(1L, "2026-05");