feat: Update styles and layout for improved UI/UX; add GEMINI project documentation

src/Core/Router.php

@@ -67,4 +67,13 @@ class Router
         http_response_code(404);
         echo '<h1>404 - Strona nie znaleziona</h1>';
     }
+
+    public static function isCurrent(string $path): bool
+    {
+        $uri = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
+        $uri = rtrim($uri, '/') ?: '/';
+        $path = rtrim($path, '/') ?: '/';
+
+        return $uri === $path;
+    }
 }