Add Czech translation and related locale files

[MioOgbeni]

This pull request adds support for the Czech language (cs-CZ) to the frontend application, including translations, locale configuration, and help documentation. The changes ensure that Czech users can select their language, see the correct flag, and access localized help content.

Czech language support and localization:

• Added Czech (cs-CZ) locale to the list of supported locales in check-locales.cjs, IntlProvider.tsx, and lang-list.json to enable Czech as a selectable language. [1] [2] [3]
• Imported Czech translations (langCs) and included them in the locale options in IntlProvider.tsx. [1] [2]
• Updated flag mapping logic to include Czechia (CZ) for the Czech locale in IntlProvider.tsx.

Czech help documentation:

• Added Czech-language help documentation files for Access Lists, Certificates, Dead Hosts, Proxy Hosts, Redirection Hosts, and Streams in src/HelpDoc/cs/. [1] [2] [3] [4] [5] [6]
• Exported Czech help documentation and registered it in the help documentation index, making it available in the application. [1] [2]

[nginxproxymanagerci]

Docker Image for build 1 is available on DockerHub:

nginxproxymanager/nginx-proxy-manager-dev:pr-5283

Note

Ensure you backup your NPM instance before testing this image! Especially if there are database changes.
This is a different docker image namespace than the official image.

Warning

Changes and additions to DNS Providers require verification by at least 2 members of the community!