feat: Phase 1 complete — Matrix login, rooms, chat, profile

- Direct m.login.password auth against matrix.m8chat.au
- Room list with unread badges, last message, timestamps
- Chat timeline (text, images, files, replies, reactions)
- Profile screen with expandable Notifications and Security sections
- Olm E2EE initialisation (web WASM bootstrap)
- Global error handler preventing Matrix SDK crashes
- GoRouter with refreshListenable (no recreation on auth change)
- Feature-first clean architecture: Riverpod + GoRouter + Drift
- Deployed to https://app2.m8chat.au

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/features/auth/domain/auth_failure.dart

@@ -0,0 +1,41 @@
+// Version: 1.0.0 | Created: 2026-04-01
+// Typed failure hierarchy for authentication errors.
+// UI maps these to human-readable messages — never expose raw exception text.
+
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'auth_failure.freezed.dart';
+
+/// All ways authentication can fail.
+@freezed
+sealed class AuthFailure with _$AuthFailure {
+  /// Username or password was incorrect.
+  const factory AuthFailure.invalidCredentials() = InvalidCredentials;
+
+  /// Could not reach the Matrix homeserver.
+  const factory AuthFailure.networkError({String? message}) = NetworkError;
+
+  /// The server returned an unexpected response.
+  const factory AuthFailure.serverError({int? statusCode, String? message}) =
+      ServerError;
+
+  /// User's account has been disabled or deactivated.
+  const factory AuthFailure.accountDisabled() = AccountDisabled;
+
+  /// An unexpected error that doesn't fit the categories above.
+  const factory AuthFailure.unknown({required String message}) = UnknownFailure;
+}
+
+/// Maps an [AuthFailure] to a user-facing string (Australian English).
+extension AuthFailureMessage on AuthFailure {
+  String get userMessage => switch (this) {
+    InvalidCredentials() => 'Incorrect username or password. Please try again.',
+    NetworkError() =>
+      'Could not connect to the server. Check your internet connection and try again.',
+    ServerError(statusCode: final code) =>
+      'The server returned an error${code != null ? ' (code $code)' : ''}. Please try again shortly.',
+    AccountDisabled() =>
+      'Your account has been disabled. Please contact the administrator.',
+    UnknownFailure(message: final msg) => 'Something went wrong: $msg',
+  };
+}