feat(cms): add maintained user guide with Súgó menu entry

- docs/felhasznaloi-utmutato.md: user guide for the website and the CMS
  (login, editing, arrays, save/validation, publish, security)
- /guide endpoint renders the markdown auth-protected via a dependency-free
  renderer (scripts/markdown-render.js) in the CMS dark theme
- new ❓ Súgó entry in the CMS bottom bar
- steering rule: the guide must be updated in the same commit as any CMS or
  website feature change

Closes MITHOME-57

scripts/markdown-render.js

@@ -0,0 +1,95 @@
+// WHY: the Content Editor runs on system Node without node_modules, so the user
+// guide (docs/felhasznaloi-utmutato.md) is rendered by this small dependency-free
+// markdown renderer instead of an external library.
+// Supported subset: headings (#..####), bold, inline code, links, ul/ol lists,
+// fenced code blocks, horizontal rules, paragraphs. HTML is escaped first.
+
+function escapeHtml(value) {
+  return String(value)
+    .replace(/&/g, '&')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;')
+    .replace(/"/g, '&quot;');
+}
+
+function renderInline(text) {
+  return escapeHtml(text)
+    .replace(/`([^`]+)`/g, '<code>$1</code>')
+    .replace(/\*\*([^*]+)\*\*/g, '<strong>$1</strong>')
+    .replace(/\[([^\]]+)\]\(([^)\s]+)\)/g, '<a href="$2" target="_blank" rel="noopener noreferrer">$1</a>');
+}
+
+function renderMarkdown(markdown) {
+  const lines = String(markdown).split('\n');
+  const out = [];
+  let listTag = null; // 'ul' | 'ol'
+  let inCode = false;
+
+  const closeList = () => {
+    if (listTag) {
+      out.push(`</${listTag}>`);
+      listTag = null;
+    }
+  };
+
+  for (const raw of lines) {
+    const line = raw.trimEnd();
+
+    if (line.trim().startsWith('```')) {
+      closeList();
+      out.push(inCode ? '</code></pre>' : '<pre><code>');
+      inCode = !inCode;
+      continue;
+    }
+    if (inCode) {
+      out.push(escapeHtml(raw));
+      continue;
+    }
+    if (!line.trim()) {
+      closeList();
+      continue;
+    }
+
+    const heading = line.match(/^(#{1,4})\s+(.*)$/);
+    if (heading) {
+      closeList();
+      const level = heading[1].length;
+      out.push(`<h${level}>${renderInline(heading[2])}</h${level}>`);
+      continue;
+    }
+    if (/^(-{3,}|\*{3,})$/.test(line.trim())) {
+      closeList();
+      out.push('<hr>');
+      continue;
+    }
+    const unordered = line.match(/^\s*[-*]\s+(.*)$/);
+    if (unordered) {
+      if (listTag !== 'ul') {
+        closeList();
+        out.push('<ul>');
+        listTag = 'ul';
+      }
+      out.push(`<li>${renderInline(unordered[1])}</li>`);
+      continue;
+    }
+    const ordered = line.match(/^\s*\d+\.\s+(.*)$/);
+    if (ordered) {
+      if (listTag !== 'ol') {
+        closeList();
+        out.push('<ol>');
+        listTag = 'ol';
+      }
+      out.push(`<li>${renderInline(ordered[1])}</li>`);
+      continue;
+    }
+
+    closeList();
+    out.push(`<p>${renderInline(line)}</p>`);
+  }
+
+  closeList();
+  if (inCode) out.push('</code></pre>');
+  return out.join('\n');
+}
+
+module.exports = { renderMarkdown, renderInline, escapeHtml };