feat(country): extend country query to support name filter

- Add support for 'name' filter in country queries
- Delegate queries with either 'usage' or 'name' filter to CountryService
- Update documentation to reflect that sorting and pagination are handled by CountryService for these specialized queries

Author: fulleni

lib/src/registry/data_operation_registry.dart

@@ -131,9 +131,11 @@ class DataOperationRegistry {
       ),
       'country': (c, uid, f, s, p) async {
         final usage = f?['usage'] as String?;
-        if (usage != null && usage.isNotEmpty) {
-          // For 'country' model with 'usage' filter, delegate to CountryService.
-          // Sorting and pagination are not supported for this specialized query.
+        final name = f?['name'] as String?;
+
+        // If either 'usage' or 'name' filter is present, delegate to CountryService.
+        // Sorting and pagination are handled by CountryService for these specialized queries.
+        if ((usage != null && usage.isNotEmpty) || (name != null && name.isNotEmpty)) {
           final countryService = c.read<CountryService>();
           final countries = await countryService.getCountries(f);
           return PaginatedResponse<Country>(
@@ -142,7 +144,8 @@ class DataOperationRegistry {
             hasMore: false, // No more items as it's a complete filtered set
           );
         } else {
-          // For standard requests, use the repository which supports pagination/sorting.
+          // For standard requests without specialized filters, use the repository
+          // which supports pagination/sorting.
           return c.read<DataRepository<Country>>().readAll(
                 userId: uid,
                 filter: f,