feat: city guide on city pages (tagline, facts, About, seasons)

Editable per city under Viator tours > Destinations. Shown above the
tours on page 1 of an unfiltered listing only; filtering and paging jump
to the results. Text recovered from the six old /tour-destination/ pages
is imported once into empty guides.

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

viator-collector/includes/class-vc-plugin.php

@@ -25,6 +25,7 @@ final class VC_Plugin {
 		VC_Cron::init();
 		VC_Display::init();
 		VC_Sections::init();
+		VC_City_Guide::init();
 	}
 
 	private function load_files() {
@@ -44,6 +45,7 @@ final class VC_Plugin {
 			'includes/class-vc-menu.php',
 			'includes/class-vc-display.php',
 			'includes/class-vc-sections.php',
+			'includes/class-vc-city-guide.php',
 		);
 
 		foreach ( $files as $file ) {