fix(database, android): improve type handling for startAt query modifier and add test for numeric startAt

packages/firebase_database/firebase_database/android/src/main/kotlin/io/flutter/plugins/firebase/database/FirebaseDatabasePlugin.kt

@@ -883,8 +883,7 @@ class FirebaseDatabasePlugin :
                 val value = modifier["value"]
                 query = when (value) {
                   is String -> query.startAt(value)
-                  is Double -> query.startAt(value)
-                  is Int -> query.startAt(value.toDouble())
+                  is Number -> query.startAt(value.toDouble())
                   is Boolean -> query.startAt(value)
                   else -> query.startAt(value.toString())
                 }

tests/integration_test/firebase_database/query_e2e.dart

@@ -31,6 +31,26 @@ void setupQueryTests() {
         expect(snapshot.value, isNull);
       });
 
+      test(
+        'streams respect orderByChild with numeric startAt',
+        () async {
+          await ref.set({
+            't1': {'timestamp': 1, 'value': 'old'},
+            't2': {'timestamp': 1000, 'value': 'current'},
+          });
+
+          final events = await ref
+              .orderByChild('timestamp')
+              .startAt(1000)
+              .onChildAdded
+              .take(1)
+              .toList();
+
+          expect(events.single.snapshot.key, 't2');
+          expect(events.single.snapshot.child('value').value, 'current');
+        },
+      );
+
       test('starts at the correct value', () async {
         await ref.set({
           'a': 1,