Add app source and tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

lib/Peach/memory/SecretStore.dart

@@ -0,0 +1,45 @@
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+
+/// Encrypted storage backed by the OS keystore: Keychain (macOS/iOS),
+/// Keystore/EncryptedSharedPreferences (Android), DPAPI (Windows) and
+/// libsecret (Linux). Server passwords live here; so does anything else the
+/// `internal_memory` brick generates with `secure: true`.
+class SecretStore {
+  static const _storage = FlutterSecureStorage(aOptions: AndroidOptions());
+
+  static String _passwordKey(String serverId) => 'peach.pw.$serverId';
+
+  /// The key this app used before it was renamed. Reads fall back to it once
+  /// and migrate the value forward, so an existing install doesn't silently
+  /// lose every stored password on upgrade.
+  static String _legacyPasswordKey(String serverId) => 'jarpilot.pw.$serverId';
+
+  Future<String?> readPassword(String serverId) async {
+    final current = await _storage.read(key: _passwordKey(serverId));
+    if (current != null) return current;
+
+    final legacy = await _storage.read(key: _legacyPasswordKey(serverId));
+    if (legacy == null) return null;
+    await _storage.write(key: _passwordKey(serverId), value: legacy);
+    await _storage.delete(key: _legacyPasswordKey(serverId));
+    return legacy;
+  }
+
+  Future<void> writePassword(String serverId, String password) =>
+      _storage.write(key: _passwordKey(serverId), value: password);
+
+  Future<void> deletePassword(String serverId) async {
+    await _storage.delete(key: _passwordKey(serverId));
+    await _storage.delete(key: _legacyPasswordKey(serverId));
+  }
+
+  // ── generic access ─────────────────────────────────────────────────────────
+  // Used by fields the `internal_memory` brick generates as secure.
+
+  static Future<String?> read(String key) => _storage.read(key: key);
+
+  static Future<void> write(String key, String value) =>
+      _storage.write(key: key, value: value);
+
+  static Future<void> delete(String key) => _storage.delete(key: key);
+}