Allow artworks to have one primary category and extra secondaries.

Keep artwork_category as membership, store a deterministic primary_category_id, and let upload plus studio pick up to five additional same-type categories without changing canonical URLs.

resources/js/lib/uploadUtils.additionalCategories.test.js

@@ -0,0 +1,14 @@
+import { describe, expect, it } from 'vitest'
+import { additionalCategoryOptions } from './uploadUtils'
+
+describe('additionalCategoryOptions', () => {
+  it('excludes the primary leaf and sorts remaining names alphabetically', () => {
+    const options = additionalCategoryOptions([
+      { id: '10', name: 'Zebra', children: [{ id: '11', name: 'Moon' }] },
+      { id: '12', name: 'Apple', children: [{ id: '13', name: 'City' }] },
+    ], '11')
+
+    expect(options.map((option) => option.name)).toEqual(['Apple', 'City', 'Zebra'])
+    expect(options.map((option) => option.id)).not.toContain('11')
+  })
+})