Migrate from HTTP API to gRPC with cqrs_services proto

- Regenerate proto stubs from correct cqrs_services.proto file
- Update GrpcCqrsApiClient to use DynamicQueryService and CommandService
- Fix type conversions for deliveries, routes, and commands
- Convert proto Timestamp to ISO8601 strings for model compatibility
- Convert string amounts to doubles for delivery orders
- Use Int64 for delivery IDs in gRPC commands

Work in progress: Timestamp conversion extension needs finalization.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/providers/providers.dart

@@ -97,8 +97,8 @@ class ApiModeConfig {
 /// )
 /// ```
 final apiModeConfigProvider = Provider<ApiModeConfig>((ref) {
-  // Default to HTTP for safety during transition
-  return ApiModeConfig.development;
+  // Use gRPC for development - HTTP backend has been deprecated
+  return ApiModeConfig.developmentGrpc;
 });
 
 // ============================================================================