Add kportal screenshot to documentation

- Add screenshot to README.md
- Add screenshot to GitHub Pages site with styling
- Include screenshot image in docs/ directory

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docs/index.html

@@ -79,6 +79,10 @@
                     <img src="https://img.shields.io/github/license/lukaszraczylo/kportal" alt="License"/>
                     <img src="https://goreportcard.com/badge/github.com/lukaszraczylo/kportal" alt="Go Report"/>
                 </div>
+                <!-- Screenshot -->
+                <div class="mt-16 max-w-4xl mx-auto">
+                    <img src="kportal-screenshot.png" alt="kportal terminal interface" class="rounded-lg shadow-2xl border border-gray-200 dark:border-gray-700"/>
+                </div>
             </div>
         </div>
     </section>