feat: implement is_critical CSS injection via CriticalCSSService

- Created CriticalCSSService (singleton) that queries BD directly in wp_head
- Service generates CSS BEFORE components render (priority 1)
- Renderers check is_critical flag and skip inline CSS if true
- Made generateCSS() public in Renderers for CriticalCSSService to use
- Removed CriticalCSSCollector pattern (timing issue with WordPress)

Flow:
1. wp_head (priority 1) → CriticalCSSService::render()
2. Service queries BD for components with visibility.is_critical=true
3. Generates CSS using Renderer->generateCSS() methods
4. Outputs: <style id="roi-critical-css">...</style>
5. When Renderers execute, they detect is_critical and omit CSS inline

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Shared/Domain/Contracts/CriticalCSSCollectorInterface.php

@@ -1,45 +0,0 @@
-<?php
-declare(strict_types=1);
-
-namespace ROITheme\Shared\Domain\Contracts;
-
-/**
- * Interface para recolectar CSS crítico de componentes above-the-fold
- *
- * RESPONSABILIDAD:
- * - Definir contrato para recolección de CSS crítico
- * - Permitir inyección en Renderers (DIP)
- *
- * UBICACIÓN: Domain (según 00.02 líneas 239-252)
- *
- * @package ROITheme\Shared\Domain\Contracts
- */
-interface CriticalCSSCollectorInterface
-{
-    /**
-     * Agregar CSS de un componente a la colección crítica
-     *
-     * @param string $componentName Identificador del componente (kebab-case)
-     * @param string $css CSS generado del componente
-     */
-    public function add(string $componentName, string $css): void;
-
-    /**
-     * Obtener todo el CSS crítico recolectado
-     *
-     * @return array<string, string> [componentName => css]
-     */
-    public function getAll(): array;
-
-    /**
-     * Renderizar CSS crítico como tag <style>
-     *
-     * @return string HTML del tag <style> o string vacío si no hay CSS
-     */
-    public function render(): string;
-
-    /**
-     * Limpiar colección (útil para tests)
-     */
-    public function clear(): void;
-}