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.

app/Http/Requests/Studio/ApplyArtworkAiAssistRequest.php

@@ -23,10 +23,13 @@ final class ApplyArtworkAiAssistRequest extends FormRequest
             'title_mode' => ['sometimes', Rule::in(['replace', 'insert'])],
             'description' => ['sometimes', 'nullable', 'string', 'max:5000'],
             'description_mode' => ['sometimes', Rule::in(['replace', 'append'])],
-            'tags' => ['sometimes', 'array', 'max:' . (int) config('tags.max_user_tags', 30)],
+            'tags' => ['sometimes', 'array', 'max:'.(int) config('tags.max_user_tags', 30)],
             'tags.*' => ['string', 'max:64'],
             'tag_mode' => ['sometimes', Rule::in(['add', 'replace', 'remove'])],
             'category_id' => ['sometimes', 'nullable', 'integer', 'exists:categories,id'],
+            'primary_category_id' => ['sometimes', 'nullable', 'integer', 'exists:categories,id'],
+            'secondary_category_ids' => ['sometimes', 'array', 'max:'.(int) config('categories.max_secondary_categories', 5)],
+            'secondary_category_ids.*' => ['integer', 'exists:categories,id'],
             'content_type_id' => ['sometimes', 'nullable', 'integer', 'exists:content_types,id'],
             'similar_actions' => ['sometimes', 'array', 'max:10'],
             'similar_actions.*.artwork_id' => ['required_with:similar_actions', 'integer'],
@@ -42,4 +45,4 @@ final class ApplyArtworkAiAssistRequest extends FormRequest
             }
         });
     }
-}
+}