[auth] Auth lockscreen fixes (#3545)

## Description

1. Removed the logout button from the lockscreen if app in without
backup state
2. Show a warning dialog when user try to set the app lock for the 1st
time

## Tests
<img
src="https://github.com/user-attachments/assets/1f12d651-12ee-4ad5-9a17-cc0c0b3c4d61"
width=200>

auth/lib/l10n/arb/app_en.arb

@@ -483,5 +483,6 @@
   "importFailureDescNew": "Could not parse the selected file.",
   "appLockNotEnabled": "App lock not enabled",
   "appLockNotEnabledDescription": "Please enable app lock from Security > App Lock",
-  "authToViewPasskey": "Please authenticate to view passkey"
+  "authToViewPasskey": "Please authenticate to view passkey",
+  "appLockOfflineModeWarning": "You have chosen to proceed without backups. If you forget your applock, you will be locked out from accessing your data."
 }

auth/lib/ui/settings/security_section_widget.dart

@@ -10,14 +10,17 @@ import 'package:ente_auth/services/user_service.dart';
 import 'package:ente_auth/theme/ente_theme.dart';
 import 'package:ente_auth/ui/account/request_pwd_verification_page.dart';
 import 'package:ente_auth/ui/account/sessions_page.dart';
+import 'package:ente_auth/ui/components/buttons/button_widget.dart';
 import 'package:ente_auth/ui/components/captioned_text_widget.dart';
 import 'package:ente_auth/ui/components/expandable_menu_item_widget.dart';
 import 'package:ente_auth/ui/components/menu_item_widget.dart';
+import 'package:ente_auth/ui/components/models/button_result.dart';
 import 'package:ente_auth/ui/components/toggle_switch_widget.dart';
 import 'package:ente_auth/ui/settings/common_settings.dart';
 import 'package:ente_auth/ui/settings/lock_screen/lock_screen_options.dart';
 import 'package:ente_auth/utils/auth_util.dart';
 import 'package:ente_auth/utils/dialog_util.dart';
+import 'package:ente_auth/utils/lock_screen_settings.dart';
 import 'package:ente_auth/utils/navigation_util.dart';
 import 'package:ente_auth/utils/platform_util.dart';
 import 'package:ente_auth/utils/toast_util.dart';
@@ -146,10 +149,27 @@ class _SecuritySectionWidgetState extends State<SecuritySectionWidget> {
         trailingIcon: Icons.chevron_right_outlined,
         trailingIconIsMuted: true,
         onTap: () async {
+          ButtonResult? result;
+          if (_config.hasOptedForOfflineMode() &&
+              LockScreenSettings.instance.getOfflineModeWarningStatus()) {
+            result = await showChoiceActionSheet(
+              context,
+              title: context.l10n.warning,
+              body: context.l10n.appLockOfflineModeWarning,
+              secondButtonLabel: context.l10n.cancel,
+              firstButtonLabel: context.l10n.ok,
+            );
+            if (result?.action == ButtonAction.first) {
+              await LockScreenSettings.instance
+                  .setOfflineModeWarningStatus(false);
+            } else {
+              return;
+            }
+          }
           if (await Configuration.instance.shouldShowLockScreen()) {
             final bool result = await requestAuthentication(
               context,
-              context.l10n.about,
+              context.l10n.authToChangeLockscreenSetting,
             );
             if (result) {
               await Navigator.of(context).push(

auth/lib/ui/tools/lock_screen.dart

@@ -33,6 +33,9 @@ class _LockScreenState extends State<LockScreen> with WidgetsBindingObserver {
   int remainingTimeInSeconds = 0;
   final _lockscreenSetting = LockScreenSettings.instance;
   late Brightness _platformBrightness;
+  final bool hasOptedForOfflineMode =
+      Configuration.instance.hasOptedForOfflineMode();
+
   @override
   void initState() {
     _logger.info("initiatingState");
@@ -53,13 +56,15 @@ class _LockScreenState extends State<LockScreen> with WidgetsBindingObserver {
     return Scaffold(
       appBar: AppBar(
         elevation: 0,
-        leading: IconButton(
-          icon: const Icon(Icons.logout_outlined),
-          color: Theme.of(context).iconTheme.color,
-          onPressed: () {
-            _onLogoutTapped(context);
-          },
-        ),
+        leading: hasOptedForOfflineMode
+            ? const SizedBox.shrink()
+            : IconButton(
+                icon: const Icon(Icons.logout_outlined),
+                color: Theme.of(context).iconTheme.color,
+                onPressed: () {
+                  _onLogoutTapped(context);
+                },
+              ),
       ),
       body: GestureDetector(
         onTap: () {

auth/lib/utils/lock_screen_settings.dart

@@ -23,6 +23,8 @@ class LockScreenSettings {
   static const keyAppLockSet = "ls_is_app_lock_set";
   static const keyHasMigratedLockScreenChanges =
       "ls_has_migrated_lock_screen_changes";
+  static const keyShowOfflineModeWarning = "ls_show_offline_mode_warning";
+
   final List<Duration> autoLockDurations = const [
     Duration(milliseconds: 650),
     Duration(seconds: 5),
@@ -47,6 +49,14 @@ class LockScreenSettings {
     await runLockScreenChangesMigration();
   }
 
+  Future<void> setOfflineModeWarningStatus(bool value) async {
+    await _preferences.setBool(keyShowOfflineModeWarning, value);
+  }
+
+  bool getOfflineModeWarningStatus() {
+    return _preferences.getBool(keyShowOfflineModeWarning) ?? true;
+  }
+
   Future<void> runLockScreenChangesMigration() async {
     if (_preferences.getBool(keyHasMigratedLockScreenChanges) != null) {
       return;