refactor(forms): move packages/form-schema → apps/app/src/composables/forms

Inlines the form-schema source folder (no package.json, alias-only)
into apps/app/src/composables/forms. Drops the @form-schema alias
from apps/app/vite.config.ts (replaced by @/composables/forms via
the existing @ alias). apps/portal vite + vitest configs keep
@form-schema as a temporary alias pointing at the new location so
portal tests/build keep working until apps/portal is removed at the
end of this PR. Two pure-logic form-schema tests moved alongside.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/app/vite.config.ts

@@ -111,9 +111,6 @@ export default defineConfig({
           import.meta.url,
         ),
       ),
-      '@form-schema': fileURLToPath(
-        new URL('../../packages/form-schema/src', import.meta.url),
-      ),
     },
   },
   server: {