feat(service): add package info service for app version retrieval

- Introduce PackageInfoService abstract class for retrieving app version
- Implement PackageInfoServiceImpl using package_info_plus package
- Add logging for successful fetch and potential failures
- Ensure null safety and platform compatibility

Author: fulleni

lib/app/services/package_info_service.dart

@@ -0,0 +1,49 @@
+import 'package:logging/logging.dart';
+import 'package:package_info_plus/package_info_plus.dart';
+
+/// {@template package_info_service}
+/// An abstract service for retrieving application package information.
+///
+/// This interface allows for mocking and provides a clean way to access
+/// platform-specific app details like version, build number, etc.
+/// {@endtemplate}
+abstract class PackageInfoService {
+  /// {@macro package_info_service}
+  const PackageInfoService();
+
+  /// Retrieves the application's version string (e.g., "1.0.0").
+  ///
+  /// Returns `null` if the version cannot be determined (e.g., on unsupported
+  /// platforms or during an error).
+  Future<String?> getAppVersion();
+}
+
+/// {@template package_info_service_impl}
+/// A concrete implementation of [PackageInfoService] using `package_info_plus`.
+/// {@endtemplate}
+class PackageInfoServiceImpl implements PackageInfoService {
+  /// {@macro package_info_service_impl}
+  PackageInfoServiceImpl({Logger? logger})
+    : _logger = logger ?? Logger('PackageInfoServiceImpl');
+
+  final Logger _logger;
+
+  @override
+  Future<String?> getAppVersion() async {
+    try {
+      final packageInfo = await PackageInfo.fromPlatform();
+      _logger.info(
+        'Successfully fetched package info. Version: ${packageInfo.version}',
+      );
+      return packageInfo.version;
+    } catch (e, s) {
+      _logger.warning(
+        'Failed to get app version from platform. '
+        'This might be expected on some platforms (e.g., web in certain contexts).',
+        e,
+        s,
+      );
+      return null;
+    }
+  }
+}