Add Environment service with platform, build mode, and app info support

finlog_app/fluttery/test/system/environment/environment_test.dart

@@ -0,0 +1,54 @@
+import 'dart:io' show Platform;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:fluttery/src/system/environment/environment_impl.dart';
+import 'package:package_info_plus/package_info_plus.dart';
+
+void main() {
+  setUp(() {
+    PackageInfo.setMockInitialValues(
+      appName: 'Test App',
+      packageName: 'com.example.testapp',
+      version: '1.2.3',
+      buildNumber: '42',
+      buildSignature: 'mock-signature',
+      installerStore: 'mock-store',
+    );
+  });
+
+  group('EnvironmentImpl', () {
+    test('defaults before loadPackageInfo()', () {
+      final env = EnvironmentImpl();
+
+      expect(env.appName, equals('Unknown'));
+      expect(env.packageName, equals('Unknown'));
+      expect(env.version, equals('0.0.0'));
+      expect(env.buildNumber, equals('0'));
+    });
+
+    test('loadPackageInfo() populates fields from PackageInfo', () async {
+      final env = EnvironmentImpl();
+      await env.loadPackageInfo();
+
+      expect(env.appName, equals('Test App'));
+      expect(env.packageName, equals('com.example.testapp'));
+      expect(env.version, equals('1.2.3'));
+      expect(env.buildNumber, equals('42'));
+    });
+
+    test('platform flags mirror dart:io Platform', () {
+      final env = EnvironmentImpl();
+
+      expect(env.isAndroid, equals(Platform.isAndroid));
+      expect(env.isIOS, equals(Platform.isIOS));
+    });
+
+    test('build mode flags reflect Flutter constants', () {
+      final env = EnvironmentImpl();
+
+      // In unit tests, this should typically be: debug=true, release/profile=false.
+      expect(env.isDebug, isTrue);
+      expect(env.isRelease, isFalse);
+      expect(env.isProfile, isFalse);
+    });
+  });
+}