feat(demo): add demo site reset with baseline snapshots and warning banner

Adds Demo Mode feature for configuring sites as demo instances with
automatic periodic reset to a saved baseline. Includes DemoResetService
for DB table + media snapshots, frontend warning banner, REST and
query-string API endpoints, admin toggles, and a Joomla Scheduled Task
plugin (plg_task_mokowaasdemo) for automatic reset.

Closes #88

Authored-by: Moko Consulting
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/script.php

@@ -36,6 +36,7 @@ class Pkg_MokowaasInstallerScript
 	{
 		$this->enablePlugin('system', 'mokowaas');
 		$this->enablePlugin('webservices', 'mokowaas');
+		$this->enablePlugin('task', 'mokowaasdemo');
 
 		// Mark MokoWaaS extensions as protected (prevents disable/uninstall at framework level)
 		$this->protectExtensions();