feat(cms): logo upload with preview, backup and audit

- 🎨 Logó page in the CMS bottom bar: replace the website header logo and
  the CMS login icon with a PNG upload (magic-byte validation, 1 MiB cap)
- the replaced logo gets a timestamped backup in .content-backups; every
  upload is audited (logo_updated)
- /logo.png?variant=header serves the header variant for the preview
- publish stages proto/public too, so logo changes ride the same
  commit+deploy pipeline as content
- route handling extracted to scripts/cms-logo.js to stay under the
  400-line limit
- integration test: upload+replace+backup, variant preview, 415/413/400,
  CSRF, auth

Closes MITHOME-65

content-editor.js

@@ -16,7 +16,8 @@ const crypto = require('crypto');
 const { validateContent } = require('./proto/src/content/schema');
 const { renderMarkdown } = require('./scripts/markdown-render');
 const { buildPublishCommand, interpretPublishResult } = require('./scripts/cms-publish');
-const { safeBackupName, listVersions, readBackupContent, buildVersionDiff } = require('./scripts/cms-versions');
+const { handleVersionRoutes, listVersions } = require('./scripts/cms-versions');
+const { LOGO_TARGETS, handleLogoRoutes } = require('./scripts/cms-logo');
 
 const PORT = Number(process.env.CONTENT_EDITOR_PORT) || 4001;
 // WHY: overridable so the publish integration test can run against a throwaway
@@ -51,6 +52,7 @@ const FILE_LABELS = {
 };
 
 const { HTML, GUIDE_PAGE, LOGIN_PAGE, VERSIONS_PAGE } = require('./scripts/cms-pages');
+const { LOGO_PAGE } = require('./scripts/cms-logo-page');
 const { validateLogin, createSessionCookie, clearSessionCookie, hasValidSession, deleteSession } = require('./scripts/cms-session');
 
 // Browser script is kept in its own file and inlined into the HTML template at render time.
@@ -104,7 +106,9 @@ const server = http.createServer(async (req, res) => {
   // Public: logo asset for the login page.
   if (req.method === 'GET' && u.pathname === '/logo.png') {
     try {
-      const logo = fs.readFileSync(path.join(__dirname, 'proto', 'public', 'mozdit_logo.png'));
+      // ?variant=header serves the website header logo (branding page preview).
+      const file = u.searchParams.get('variant') === 'header' ? LOGO_TARGETS.header : LOGO_TARGETS.icon;
+      const logo = fs.readFileSync(path.join(__dirname, 'proto', 'public', file));
       res.writeHead(200, { 'Content-Type': 'image/png', 'Cache-Control': 'public, max-age=3600' });
       res.end(logo);
     } catch {
@@ -304,55 +308,24 @@ const server = http.createServer(async (req, res) => {
     return;
   }
 
-  // GET /versions — backup list + optional diff view (browser page, session-auth).
-  if (req.method === 'GET' && u.pathname === '/versions') {
-    const versions = listVersions(BACKUP_DIR, activeFile);
-    let diff = null;
-    const showRaw = u.searchParams.get('show');
-    if (showRaw) {
-      const safe = safeBackupName(activeFile, showRaw);
-      if (safe) {
-        try {
-          diff = buildVersionDiff(BACKUP_DIR, FILES[activeFile], activeFile, safe);
-        } catch { /* unreadable backup: render list only */ }
-      }
-    }
-    res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8', 'Cache-Control': 'no-store' });
-    res.end(VERSIONS_PAGE(activeFile, FILE_LABELS[activeFile] || activeFile, versions, diff, CSRF_TOKEN));
-    return;
-  }
+  // GET /versions + POST /restore — handled in scripts/cms-versions.js.
+  if (handleVersionRoutes({
+    req, res, u, activeFile,
+    backupDir: BACKUP_DIR,
+    currentFile: FILES[activeFile],
+    validate: validateContent,
+    writeAudit, clientAddress, user: CMS_USER,
+    versionsPage: (fileKey, diff) => VERSIONS_PAGE(fileKey, FILE_LABELS[fileKey] || fileKey, listVersions(BACKUP_DIR, fileKey), diff, CSRF_TOKEN),
+  })) return;
 
-  // POST /restore — restore a backup; the current state is backed up first,
-  // so the restore itself is reversible. Schema validation guards against
-  // restoring a structurally broken backup.
-  if (req.method === 'POST' && u.pathname === '/restore') {
-    const backup = safeBackupName(activeFile, u.searchParams.get('backup') || '');
-    if (!backup) {
-      res.writeHead(400, { 'Content-Type': 'application/json' });
-      res.end(JSON.stringify({ ok: false, error: 'Érvénytelen mentésnév.' }));
-      return;
-    }
-    try {
-      const content = readBackupContent(BACKUP_DIR, backup);
-      const data = JSON.parse(content);
-      const validation = validateContent(activeFile, data);
-      if (!validation.ok) {
-        writeAudit('version_restored', { clientAddress, user: CMS_USER, file: activeFile, backup, result: 'validation_failed' });
-        res.writeHead(422, { 'Content-Type': 'application/json' });
-        res.end(JSON.stringify({ ok: false, error: 'A mentés nem felel meg a sémának: ' + validation.errors.join('; ') }));
-        return;
-      }
-      backupAndWriteAtomically(FILES[activeFile], data, BACKUP_DIR);
-      writeAudit('version_restored', { clientAddress, user: CMS_USER, file: activeFile, backup, result: 'ok' });
-      res.writeHead(200, { 'Content-Type': 'application/json' });
-      res.end(JSON.stringify({ ok: true }));
-    } catch (e) {
-      writeAudit('version_restored', { clientAddress, user: CMS_USER, file: activeFile, backup, result: 'error' });
-      res.writeHead(500, { 'Content-Type': 'application/json' });
-      res.end(JSON.stringify({ ok: false, error: e.message }));
-    }
-    return;
-  }
+  // GET /branding + POST /logo — handled in scripts/cms-logo.js.
+  if (handleLogoRoutes({
+    req, res, u,
+    publicDir: path.join(__dirname, 'proto', 'public'),
+    backupDir: BACKUP_DIR,
+    writeAudit, clientAddress, user: CMS_USER,
+    logoPage: () => LOGO_PAGE(CSRF_TOKEN),
+  })) return;
 
   // GET / — editor UI
   let message = null;