Add support for private and hashtag channels in localization and channel management

- Updated Polish, Portuguese, Slovak, Slovenian, Swedish, and Chinese localization files to include new strings for creating and joining private channels, as well as joining hashtag channels.
- Enhanced the channel management UI to allow users to create and join private channels, join public channels, and join channels via hashtags.
- Implemented PSK derivation from hashtags using SHA256 in the Channel model.
- Improved the translation script to handle missing keys and translate all locales efficiently.

lib/l10n/app_localizations_en.dart

@@ -818,6 +818,43 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get channels_sortUnread => 'Unread';
 
+  @override
+  String get channels_createPrivateChannel => 'Create a Private Channel';
+
+  @override
+  String get channels_createPrivateChannelDesc => 'Secured with a secret key.';
+
+  @override
+  String get channels_joinPrivateChannel => 'Join a Private Channel';
+
+  @override
+  String get channels_joinPrivateChannelDesc => 'Manually enter a secret key.';
+
+  @override
+  String get channels_joinPublicChannel => 'Join the Public Channel';
+
+  @override
+  String get channels_joinPublicChannelDesc => 'Anyone can join this channel.';
+
+  @override
+  String get channels_joinHashtagChannel => 'Join a Hashtag Channel';
+
+  @override
+  String get channels_joinHashtagChannelDesc =>
+      'Anyone can join hashtag channels.';
+
+  @override
+  String get channels_scanQrCode => 'Scan a QR Code';
+
+  @override
+  String get channels_scanQrCodeComingSoon => 'Coming soon';
+
+  @override
+  String get channels_enterHashtag => 'Enter hashtag';
+
+  @override
+  String get channels_hashtagHint => 'e.g. #team';
+
   @override
   String get chat_noMessages => 'No messages yet';