[WIP] Updated `cs` messages following the lindat v5 and clarin-dspace v7 instance

[milanmajchrak]

Description

Some cs messages added by NTK in this commit: https://github.com/DSpace/dspace-angular/commit/ca7a9cf12007355317006c7c55a2fbbd31db1d6b weren't 100% correct. This PR aims to resolve some mistakes or start a discussion about the correct translation.

Instructions for Reviewers

Check the correct translation to Czech language.

Checklist

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• [ ] My PR is created against the main branch of code (unless it is a backport or is fixing an issue specific to an older branch).
• [ ] My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• [ ] My PR passes ESLint validation using yarn lint
• [ ] My PR doesn't introduce circular dependencies (verified via yarn check-circ-deps)
• [ ] My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• [ ] My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• [ ] My PR aligns with Accessibility guidelines if it makes changes to the user interface.
• [ ] My PR uses i18n (internationalization) keys instead of hardcoded English text, to allow for translations.
• [ ] My PR includes details on how to test it. I've provided clear instructions to reviewers on how to successfully test this fix or feature.
• [ ] If my PR includes new libraries/dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.
• [ ] If my PR includes new features or configurations, I've provided basic technical documentation in the PR itself.
• [ ] If my PR fixes an issue ticket, I've linked them together.