Content: publish/hide chapters, sections and articles

- migration V5 adds published flag (default true) to chapters/sections/articles
- ContentService: tree(includeHidden) filters, treeAll(), findArticle(includeHidden),
  set*Published; public tree/article expose only published items
- admin API: GET /tree/all, GET /all/{chapter}/{section}/{article}, PUT
  /{chapters|sections|articles}/{id}/published
- web: learn pages for admins load the full tree, show "скрыто" badges and
  publish/hide buttons for every chapter, section and article; hidden articles
  open in preview for admins, guests get "not found"; article view carries
  published flag

web/src/main/resources/templates/learn/article.html

@@ -13,7 +13,10 @@
         <span class="nav-sep">/</span>
         <span th:text="${article.title}">Статья</span>
     </nav>
-    <h1 class="page-title" th:text="${article.title}">Статья</h1>
+    <h1 class="page-title">
+        <span th:text="${article.title}">Статья</span>
+        <span th:if="${!article.published}" class="badge badge-warn ml-2">скрыто от студентов</span>
+    </h1>
     <div class="card card-body md-body" th:utext="${article.bodyHtml}"></div>
 </div>
 </body>

web/src/main/resources/templates/learn/chapter.html

@@ -8,7 +8,10 @@
         <span class="nav-sep">/</span>
         <span th:text="${chapter.title}">Глава</span>
     </nav>
-    <h1 class="page-title" th:text="${chapter.title}">Глава</h1>
+    <h1 class="page-title">
+        <span th:text="${chapter.title}">Глава</span>
+        <span th:if="${!chapter.published}" class="badge badge-warn ml-2">скрыто</span>
+    </h1>
 
     <div th:if="${#lists.isEmpty(chapter.sections)}" class="card card-body text-muted">
         В этой главе пока нет разделов.
@@ -17,11 +20,13 @@
     <div th:each="section : ${chapter.sections}" class="card card-body mb-4">
         <h2 class="group-title">
             <a th:href="@{/learn/{c}/{s}(c=${chapter.slug}, s=${section.slug})}" th:text="${section.title}">Раздел</a>
+            <span th:if="${!section.published}" class="badge badge-warn">скрыто</span>
         </h2>
         <ul class="list-pad text-sm">
             <li th:each="article : ${section.articles}">
                 <a th:href="@{/learn/{c}/{s}/{a}(c=${chapter.slug}, s=${section.slug}, a=${article.slug})}"
                    th:text="${article.title}">Статья</a>
+                <span th:if="${!article.published}" class="badge badge-warn ml-1">скрыто</span>
             </li>
             <li th:if="${#lists.isEmpty(section.articles)}" class="text-muted">Статей пока нет</li>
         </ul>

web/src/main/resources/templates/learn/index.html

@@ -11,6 +11,10 @@
             <button class="btn btn-secondary" type="button" onclick="openModal('modal-new-chapter')">+ Глава</button>
         </div>
     </div>
+    <div th:if="${currentUser != null and currentUser.admin}" class="card card-body text-sm text-muted mb-4">
+        Режим администратора: скрытые главы, разделы и статьи помечены значком «скрыто»
+        и видны только вам. Кнопка-значок публикует материал для студентов или снова скрывает его.
+    </div>
     <div th:if="${notice}" class="alert alert-success" th:text="${notice}"></div>
     <div th:if="${error}" class="alert alert-error" th:text="${error}"></div>
 
@@ -25,8 +29,19 @@
         </summary>
         <div class="card-body acc-body">
             <div class="flex flex-wrap items-center justify-between gap-4 mb-4">
-                <h2 class="section-title" th:text="${chapter.title}">Глава</h2>
-                <div th:if="${currentUser != null and currentUser.admin}" class="flex flex-wrap gap-2">
+                <h2 class="section-title m-0">
+                    <span th:text="${chapter.title}">Глава</span>
+                    <span th:if="${!chapter.published}" class="badge badge-warn ml-2">скрыто</span>
+                </h2>
+                <div th:if="${currentUser != null and currentUser.admin}" class="flex flex-wrap items-center gap-2">
+                    <form class="inline-form" th:action="@{/admin/content/chapters/toggle-published}" method="post">
+                        <input type="hidden" name="_csrf" th:value="${csrfToken}">
+                        <input type="hidden" name="id" th:value="${chapter.id}">
+                        <input type="hidden" name="published" th:value="${!chapter.published}">
+                        <button class="btn btn-sm" type="submit"
+                                th:classappend="${chapter.published} ? 'btn-secondary' : 'btn-primary'"
+                                th:text="${chapter.published} ? 'Скрыть главу' : 'Опубликовать главу'">Скрыть главу</button>
+                    </form>
                     <button class="btn btn-secondary btn-sm" type="button"
                             th:data-modal="|modal-rename-chapter-${chapter.id}|" onclick="openModalData(this)">Переименовать</button>
                     <form th:action="@{/admin/content/chapters/{id}/delete(id=${chapter.id})}" method="post"
@@ -44,11 +59,20 @@
                     <h3 class="group-title m-0">
                         <span class="sub-arrow" aria-hidden="true"></span>
                         <a th:href="@{/learn/{c}/{s}(c=${chapter.slug}, s=${section.slug})}" th:text="${section.title}">Раздел</a>
+                        <span th:if="${!section.published}" class="badge badge-warn ml-2">скрыто</span>
                     </h3>
                 </summary>
                 <div class="flex flex-wrap items-center justify-between gap-4 sub-actions">
                     <div class="spacer"></div>
                     <div th:if="${currentUser != null and currentUser.admin}" class="flex flex-wrap gap-2">
+                        <form class="inline-form" th:action="@{/admin/content/sections/toggle-published}" method="post">
+                            <input type="hidden" name="_csrf" th:value="${csrfToken}">
+                            <input type="hidden" name="id" th:value="${section.id}">
+                            <input type="hidden" name="published" th:value="${!section.published}">
+                            <button class="btn btn-sm" type="submit"
+                                    th:classappend="${section.published} ? 'btn-secondary' : 'btn-primary'"
+                                    th:text="${section.published} ? 'Скрыть раздел' : 'Опубликовать раздел'">Скрыть раздел</button>
+                        </form>
                         <button class="btn btn-secondary btn-sm" type="button"
                                 th:data-modal="|modal-rename-section-${section.id}|" onclick="openModalData(this)">Переименовать</button>
                         <button class="btn btn-secondary btn-sm" type="button"
@@ -64,7 +88,16 @@
                     <li th:each="article : ${section.articles}" class="flex items-center gap-2">
                         <a th:href="@{/learn/{c}/{s}/{a}(c=${chapter.slug}, s=${section.slug}, a=${article.slug})}"
                            th:text="${article.title}">Статья</a>
+                        <span th:if="${!article.published}" class="badge badge-warn">скрыто</span>
                         <th:block th:if="${currentUser != null and currentUser.admin}">
+                            <form class="inline-form" th:action="@{/admin/content/articles/toggle-published}" method="post">
+                                <input type="hidden" name="_csrf" th:value="${csrfToken}">
+                                <input type="hidden" name="id" th:value="${article.id}">
+                                <input type="hidden" name="published" th:value="${!article.published}">
+                                <button class="btn btn-sm" type="submit"
+                                        th:classappend="${article.published} ? 'btn-secondary' : 'btn-primary'"
+                                        th:text="${article.published} ? 'Скрыть' : 'Опубликовать'">Скрыть</button>
+                            </form>
                             <button class="btn btn-secondary btn-sm" type="button"
                                     th:data-modal="|modal-edit-article-${article.id}|" onclick="openModalData(this)">Править</button>
                             <form class="inline-form" th:action="@{/admin/content/articles/{id}/delete(id=${article.id})}" method="post"

web/src/main/resources/templates/learn/section.html

@@ -10,14 +10,20 @@
         <span class="nav-sep">/</span>
         <span th:text="${section.title}">Раздел</span>
     </nav>
-    <h1 class="page-title" th:text="${section.title}">Раздел</h1>
+    <h1 class="page-title">
+        <span th:text="${section.title}">Раздел</span>
+        <span th:if="${!section.published}" class="badge badge-warn ml-2">скрыто</span>
+    </h1>
     <div class="card card-flush">
         <table>
             <thead><tr><th>Статья</th></tr></thead>
             <tbody>
             <tr th:each="article : ${section.articles}">
-                <td><a th:href="@{/learn/{c}/{s}/{a}(c=${chapter.slug}, s=${section.slug}, a=${article.slug})}"
-                       th:text="${article.title}">—</a></td>
+                <td>
+                    <a th:href="@{/learn/{c}/{s}/{a}(c=${chapter.slug}, s=${section.slug}, a=${article.slug})}"
+                       th:text="${article.title}">—</a>
+                    <span th:if="${!article.published}" class="badge badge-warn ml-1">скрыто</span>
+                </td>
             </tr>
             <tr th:if="${#lists.isEmpty(section.articles)}"><td class="empty">Статей пока нет.</td></tr>
             </tbody>