refactor: rename favorite renaming action to "Change sidebar label"

Address review feedback on the sidebar favorite renaming feature:

- Context menu item and dialog title now share the same
  "change-sidebar-label" translation key
- Rename NavMenuAction::RenameFavorite and DialogPage::RenameFavorite
  to ChangeSidebarLabel, with the dialog field renamed to "label"
- Rename Favorite::with_name to Favorite::with_label
- Dialog confirm button now uses the existing "save" key instead of
  "rename-confirm"
- Replace the "rename-favorite"/"favorite-name" keys with
  "sidebar-label" in en and pt-BR translations

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YRJDQDBKhCqipbcZm7U1v9

i18n/pt-BR/cosmic_files.ftl

@@ -109,10 +109,9 @@ permanently-delete-warning = Deseja realmente excluir permanentemente { $target
 rename-file = Renomear arquivo
 rename-folder = Renomear pasta
 
-## Rename Favorite Dialog
+## Change Sidebar Label Dialog
 
-rename-favorite = Renomear item da barra lateral
-favorite-name = Nome do item
+sidebar-label = Rótulo da barra lateral
 
 ## Replace Dialog
 
@@ -370,6 +369,7 @@ open-in-terminal = Abrir no terminal
 move-to-trash = Mover para a lixeira
 restore-from-trash = Restaurar da lixeira
 remove-from-sidebar = Remover da barra lateral
+change-sidebar-label = Alterar rótulo na barra lateral
 sort-by-name = Ordenar por nome
 sort-by-modified = Ordenar por data de modificação
 sort-by-size = Ordenar por tamanho