[Bug] Round system.datetime grid filter to whole day

`DateTimeFilter::apply` passed `roundToDay=false` to the trait, which makes
GDI's `DateFilter` collapse `gte` and `lte` to the same instant for `on`
queries — never matching a stored datetime with a non-zero time component.
The filter UI is date-only, so whole-day match is the right semantic.
`DateFilter` (for `system.date`) already passes `true`; this aligns
`DateTimeFilter`.

Author: markus-moser

src/DataIndex/Filter/DateTimeFilter.php

@@ -32,8 +32,9 @@ public function apply(mixed $parameters, QueryInterface $query): QueryInterface
             return $query;
         }
 
+        // Date-only filter UI — match whole days, not exact instants.
         foreach ($parameters->getColumnFilterByType(ColumnType::SYSTEM_DATETIME->value) as $column) {
-            $query = $this->applySystemDatetimeFilter($column, $query, false);
+            $query = $this->applySystemDatetimeFilter($column, $query, true);
         }
 
         return $query;