style: normalize headers, overtype editor rounded corners, remove duplicate cover preview, thesis-add-header grid layout, subtitle below header with top gradient

app/public/admin/edit.php

@@ -19,7 +19,7 @@ $autofocusField = App::consumeAutofocus();
 
 // Form help blocks for editable généralités
 $helpBlocks = Database::getInstance()->getAllFormHelpBlocks();
-$helpFn = fn(string $key) => $helpBlocks[$key]['content'] ?? '';
+$helpFn = fn(string $key) => empty($helpBlocks[$key]['enabled']) ? '' : ($helpBlocks[$key]['content'] ?? '');
 
 function old($key, $default = "") {
     global $formData;