Migrate NFS pages to HeaderPage

Always render the plugin header for page blueprints and move page-level actions into the Backstage UI header pattern for affected NFS pages.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

.changeset/nfs-header-foundations.md

@@ -0,0 +1,7 @@
+---
+'@backstage/frontend-plugin-api': patch
+'@backstage/plugin-app': patch
+'@backstage/ui': patch
+---
+
+Pages created with `PageBlueprint` now render the plugin header by default in the new frontend system, and `HeaderPage` now supports subtitles for page-level headers.

.changeset/nfs-header-page-migrations.md

@@ -0,0 +1,16 @@
+---
+'@backstage/plugin-api-docs': patch
+'@backstage/plugin-auth': patch
+'@backstage/plugin-catalog': patch
+'@backstage/plugin-catalog-graph': patch
+'@backstage/plugin-catalog-import': patch
+'@backstage/plugin-catalog-unprocessed-entities': patch
+'@backstage/plugin-devtools': patch
+'@backstage/plugin-notifications': patch
+'@backstage/plugin-scaffolder': patch
+'@backstage/plugin-search': patch
+'@backstage/plugin-techdocs': patch
+'@backstage/plugin-user-settings': patch
+---
+
+New frontend system pages now use the default plugin header together with `HeaderPage` instead of the legacy core page header pattern.