DOM-Modernisierung: \Dom\HTMLDocument (PHP 8.4) statt libxml-Workarounds

[Copilot]

Replaces all legacy DOMDocument + @loadHTML() patterns with PHP 8.4's native \Dom\HTMLDocument and \Dom\XMLDocument APIs, eliminating error-suppression hacks, the deprecated utf8_decode() call, and global libxml_use_internal_errors() side-effects.

PHP version

• package.yml: php: '>=8.0' → php: '>=8.4'

MFormParser.php

• use DOMDocument / DOMElement / DOMNodeList → use Dom\HTMLDocument
• All DOM instantiation patterns replaced:

// Before
$dom = new DOMDocument('1.0', 'utf-8');
@$dom->loadHTML('<?xml encoding="utf-8" ?>' . $html);

// After
$dom = HTMLDocument::createFromString($html, LIBXML_NOERROR);

• utf8_decode($html) removed from all loadHTML call-sites
• getBodyInner() rewritten — drops C14N + regex body extraction in favour of $dom->body?->innerHTML / $element->outerHTML
• Method signatures updated: DOMDocument → HTMLDocument, DOMElement → \Dom\Element, DOMNodeList<DOMElement> → \Dom\HTMLCollection
• instanceof DOMElement → instanceof \Dom\Element

HtmlToSvgConverter.php

• Unused $this->dom property removed (was @phpstan-ignore property.onlyWritten)
• libxml_use_internal_errors(true) removed from constructor
• $this->svg migrated from DOMDocument to Dom\XMLDocument::createEmpty('1.0', 'UTF-8')
• saveXML() → saveXml() (PHP 8.4 naming)
• Type hints: \DOMElement / \DOMNode → \Dom\Element / \Dom\Node