Harden KantSites after the security review

- The installer only opens with a per-installation key that install.php
  creates and shows; the key is deleted with the first account.
- Lock files keep .env, the database, backups and logs out of reach when a
  domain points at the project folder instead of public/.
- Linked sections render by their own schema version, so an old section
  cannot carry unfiltered HTML into a newer page.
- Editors no longer move, trash or change areas and post data of published
  pages; a scheduled publication goes live with the revision that was
  scheduled (migration 20261012000100).
- Form stamps are bound to their form, IPv6 senders count per /64, and a
  flood per form or overall stops storing with a visible message.
- The consent redirect rejects control characters, update targets must look
  like 1.2.3, and own CSS cannot reach outside its block.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/build-release.php

@@ -67,7 +67,7 @@ echo "Fassung {$version}\n";
 // migrations.php und cli-config.php gehoeren dazu: ohne die erste findet Doctrine beim
 // Einrichten keine Migrationsliste und bricht mit "configuration file does not exist" ab - genau
 // dort, wo eine frische Installation ihre Tabellen anlegen will.
-$include = ['bin', 'config', 'migrations', 'plugins', 'public', 'src', 'templates', 'composer.json', 'composer.lock', 'migrations.php', 'cli-config.php', 'VERSION', 'README.md', '.env.example'];
+$include = ['bin', 'config', 'migrations', 'plugins', 'public', 'src', 'templates', 'composer.json', 'composer.lock', 'migrations.php', 'cli-config.php', 'VERSION', 'README.md', '.env.example', '.htaccess'];
 $skip = ['.git', '.github', '.claude', '.gitattributes', '.gitignore', '.env.lock', '.php-cs-fixer.cache', 'node_modules', 'var', 'tests', 'scripts', 'reports', 'phpunit.xml.dist', '.php-cs-fixer.dist.php', 'package.json', 'package-lock.json', 'AGENTS.md', 'ENTWICKLUNGSPLAN.md', 'docs', 'composer.phar', '.venv', 'vendor', 'phpunit.cache', 'migrations.php.bak'];
 
 $copy = static function (string $from, string $to) use (&$copy, $skip): int {
@@ -116,6 +116,8 @@ if (!$ok) {
     exit(1);
 }
 echo 'vendor/ gebaut'.($flags ? ' ohne Entwicklungspakete' : ' MIT Entwicklungspaketen')."\n";
+// vendor/ gehört nicht ins Netz, auch wenn die Domain falsch zeigt (ADR 116).
+copy($root.'/config/schutz/sperren.htaccess', $staging.'/vendor/.htaccess');
 
 // The environment file is not part of a release: it holds the secret of one installation.
 foreach (['.env.local', '.env.prod.local'] as $secret) {