feat(i18n): add Danish(da) locale support (#1772)

* feat(i18n): Add Danish locale support

- Add complete Danish (da) translations for calendar notifications
- Use modern Danish terminology and professional language
- Include proper Danish date/time formatting (kl. notation)
- Follow contemporary Danish UI conventions

* feat(i18n): Add Danish language support to Language enum

crates/nlp/src/language/mod.rs

@@ -128,6 +128,7 @@ impl Language {
             "it" => Language::Italian,
             "fr" => Language::French,
             "de" => Language::German,
+            "da" => Language::Danish,
             "ru" => Language::Russian,
             "zh" => Language::Mandarin,
             "ja" => Language::Japanese,