Generate content in an explicitly selected language

[hranasit]

Ensure that generated content always uses an explicitly selected language. The language should either be detected automatically from the selected template or chosen manually by the user in the UI.

The selected language must be included explicitly in the generation prompt to prevent language inconsistencies in the output.

[hranasit]

Created based on #95, tested prompt is already in the branch https://github.com/ds-wizard/ai-document-plugin/tree/feature/137-generate-content-in-an-explicitly-selected-language with explicitly selected czech language

[MatejFrnka]

Take the language value from the project data (available since 4.33, maybe support older versions as well).
Display it to the user, allow the user to change this value to something custom if needed.

• Also test if the generated dmps make sense when the source is in different language than what the user requested.