fix(comments): align image upload with Zibll

Unify comment image upload settings, REST permissions, preview, progress,
and response handling while removing obsolete compatibility paths.

.gitignore

@@ -46,6 +46,7 @@
 !/tests/widget-system/front-submit-editor-contract.test.cjs
 !/tests/widget-system/comment-smilies-removal-contract.test.cjs
 !/tests/widget-system/comment-children-list-reset-contract.test.cjs
+!/tests/widget-system/comment-image-upload-contract.test.cjs
 !/tests/widget-system/pay-card-contract.test.cjs
 !/tests/widget-system/circular-button-icon-margin-contract.test.cjs
 !/tests/widget-system/frontend-lifecycle-contract.test.cjs