Fix pre-existing syntax errors in analytics and REST API classes

- analytics.php line 38: mismatched quotes on session_id array key
- analytics.php line 246: invalid escape before concatenation operator
- analytics.php line 250: COuNT typo → COUNT
- analytics.php line 252: NULIF typo → NULLIF
- rest-api.php line 54: stray # commenting out foreach variable

These bugs predate the content filter feature but were caught by the
new CI pipeline's PHP lint job.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

includes/class-peptide-news-rest-api.php

@@ -51,7 +51,7 @@ class Peptide_News_Rest_API {
             '/analytics/export'  => 'get_export',
         );
 
-        foreach( #$analytics_routes as $route => $callback ) {
+        foreach ( $analytics_routes as $route => $callback ) {
             register_rest_route( self::API_NAMESPACE, $route, array(
                 'methods'             => 'GET',
                 'callback'            => array( $this, $callback ),