feat(API): media library

features/delete_article_keeps_images.feature

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+Feature: Deleting an article never deletes images
+
+  As an authenticated RenewCMS user
+  I want deleting an article to leave the media library alone
+  So that an image used by other articles, or waiting in the library, is never lost
+
+  Background:
+    Given images belong to the library and internal/domain/article.Article carries no Images
+    And DeleteArticleUseCase depends only on article.Repository and calls its Delete
+    And api/dependecyInjection.go builds useCases.NewDeleteArticleUseCase(repos.ArticleRepo)
+    And DELETE /v1/article/{id} stays behind the same jwtauth group, answering 204 with an
+      empty body, 404 with apperr.ArticleNotFoundErrorMessage for errors.Is(err,
+      article.ErrArticleNotFound), and the generic 500 "Failed to delete article" otherwise
+
+  Scenario: Deleting an article leaves every image it used
+    Given a valid jwt cookie for user 1
+    And article 1 whose body contains the urls of images 10 and 11
+    And the image repository contains images 10 and 11
+    When the client sends DELETE /v1/article/1
+    Then the response status is 204
+    And the article repository no longer contains article 1
+    And the image repository still contains images 10 and 11 and Delete was never called
+
+  Scenario: Deleting an unknown article is 404 and touches no image
+    Given a valid jwt cookie for user 1 and no article 9999
+    When the client sends DELETE /v1/article/9999
+    Then the response status is 404 and the body is "Article not found"
+    And the image repository is untouched
+
+  Scenario: Deleting still requires authentication
+    Given no jwt cookie
+    When the client sends DELETE /v1/article/1
+    Then the response status is 401 and article 1 and image 10 still exist
+
+  Scenario: An article repository failure is 500 and everything stays
+    Given the article repository's Delete fails
+    When the client sends DELETE /v1/article/1 with a valid cookie
+    Then the response status is 500 and the body is "Failed to delete article"
+    And the image repository is untouched