fix(i18n): add missing messages to Norwegian (nb_NO, nn_NO) locales

The Norwegian Bokmål (`nb_NO`) and Nynorsk (`nn_NO`) locales were missing four message keys that exist in `en.json`: - `_default` - `integer` - `length` - `url` This adds idiomatic translations for all four to both locales, so Norwegian users get proper messages for these rules instead of falling back to the rule name. I'm a native Norwegian speaker and reviewed both. Translation was done with AI assistance (Claude) and checked by me; I'm more fluent in Bokmål than Nynorsk, so a second Nynorsk pass is welcome.