Fix: Use simple HTML output to test routing

- Changed AdminController to use simple echo/exit instead of TemplateResponse
  - Eliminates TemplateResponse complexity
  - Direct HTML output for debugging
- Simplified routes.php to single admin route
  - Removed test route (no longer needed)
  - Simple GET only route
- Simplified Application.php
  - Removed resource loading
  - Minimal bootstrap

If this shows 'Controller is working' page, routing is confirmed working.
If it still redirects to dashboard, it's a Nextcloud routing issue.

This is a minimal test version to confirm routing works before building full UI.

analyticshub/appinfo/Application.php

@@ -5,7 +5,6 @@ declare(strict_types=1);
 namespace OCA\AnalyticsHub\AppInfo;
 
 use OCP\AppFramework\App;
-use OCP\Util;
 
 /**
  * Application class for Mini-CMO Analytics Hub
@@ -18,8 +17,6 @@ class Application extends App {
     public function __construct(array $urlParams = []) {
         parent::__construct(self::APP_ID, $urlParams);
 
-        // Load scripts and styles for admin page
-        Util::addStyle(self::APP_ID, 'admin');
-        Util::addScript(self::APP_ID, 'admin');
+        // No resources to load for simple test
     }
 }