(fix): handle millisecond timestamp strings in Mongo castingBefore

When castingBefore receives a numeric string (millisecond timestamp)
for a Datetime column, pass it directly to UTCDateTime instead of
routing through NativeDateTime which rejects raw numeric strings.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: abnegate

src/Database/Adapter/Mongo.php

@@ -2532,7 +2532,11 @@ public function castingBefore(Document $collection, Document $document): Documen
                         if (! ($node instanceof UTCDateTime)) {
                             /** @var mixed $node */
                             $nodeStr = \is_string($node) ? $node : (\is_scalar($node) ? (string) $node : '');
-                            $node = new UTCDateTime(new NativeDateTime($nodeStr));
+                            if (\is_numeric($nodeStr)) {
+                                $node = new UTCDateTime((int) $nodeStr);
+                            } else {
+                                $node = new UTCDateTime(new NativeDateTime($nodeStr));
+                            }
                         }
                         break;
                     case ColumnType::Object: