fix: Block shortcode rendering during page template loading

- Added $loading_page_template flag in TemplateLoader
- template-wrapper.php sets flag before loading theme header/footer
- Shortcodes::render_template() returns early if flag is set
- Prevents recursion from theme components, widgets, or other plugins

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

includes/Frontend/template-wrapper.php

@@ -13,7 +13,10 @@ if ( ! defined( 'ABSPATH' ) ) {
 use WP_FediStream\Plugin;
 use WP_FediStream\Frontend\TemplateLoader;
 
-// Enter shortcode context to prevent recursive shortcode processing in post content.
+// Enter page template loading mode - this completely blocks nested FediStream rendering.
+TemplateLoader::enter_page_template_loading();
+
+// Also enter shortcode context to prevent recursive shortcode processing in post content.
 TemplateLoader::enter_shortcode_context();
 
 // Get template context.
@@ -78,7 +81,8 @@ get_header();
 </main>
 
 <?php
-// Exit shortcode context.
+// Exit shortcode context and page template loading mode.
 TemplateLoader::exit_shortcode_context();
+TemplateLoader::exit_page_template_loading();
 
 get_footer();