OTA Update attempt

lib/models/app_version.dart

@@ -0,0 +1,59 @@
+/// Represents a row in the ``app_versions`` table on the server.  The
+/// `AppUpdateService` fetches the most recent entry and compares it against the
+/// running application's build number.
+class AppVersion {
+  /// Incrementing integer that matches the Android `versionCode`.
+  final int versionCode;
+
+  /// If the device is running a build number that is *strictly less* than this
+  /// value the update is considered "forced" and the user cannot continue
+  /// using the existing install.
+  final int minVersionRequired;
+
+  /// A publicly‑accessible URL pointing at an APK stored in Supabase Storage.
+  final String downloadUrl;
+
+  /// Markdown/plaintext release notes that will be shown in the dialog.
+  final String releaseNotes;
+
+  AppVersion({
+    required this.versionCode,
+    required this.minVersionRequired,
+    required this.downloadUrl,
+    required this.releaseNotes,
+  });
+
+  factory AppVersion.fromMap(Map<String, dynamic> map) {
+    return AppVersion(
+      versionCode: map['version_code'] as int,
+      minVersionRequired: map['min_version_required'] as int,
+      downloadUrl: map['download_url'] as String,
+      releaseNotes: map['release_notes'] as String? ?? '',
+    );
+  }
+}
+
+/// Helper type returned by ``AppUpdateService.checkForUpdate`` so callers can
+/// decide how to present the UI.
+class AppUpdateInfo {
+  /// The version that was returned from ``app_versions``.  ``null`` when the
+  /// table was empty (should not happen in normal operation).
+  final AppVersion? latestVersion;
+
+  /// Current build number as reported by ``package_info_plus``.
+  final int currentBuildNumber;
+
+  /// ``true`` when ``currentBuildNumber < latestVersion.versionCode``.
+  final bool isUpdateAvailable;
+
+  /// ``true`` when ``currentBuildNumber < latestVersion.minVersionRequired``
+  /// (regardless of whether there is a newer release available).
+  final bool isForceUpdate;
+
+  AppUpdateInfo({
+    required this.currentBuildNumber,
+    required this.latestVersion,
+    required this.isUpdateAvailable,
+    required this.isForceUpdate,
+  });
+}