Fix missing changesets and tsc errors from CI

Add changesets for plugin-app and plugin-catalog-graph. Fix cross-style
merge test to use direct schema values with configSchema instead of
factory functions.

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

.changeset/app-configschema-migration.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-app': patch
+---
+
+Migrated `AppLanguageApi` extension to use the new `configSchema` option.

.changeset/catalog-graph-docs-update.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-catalog-graph': patch
+---
+
+Updated `README-alpha.md` extension examples to use current APIs.