feat: add user search page with styled form, result list, and fancy-button submit

- Replace generic-form with custom form containing text input and fancy-button
- Add CSS for anchor links, chat-area list items, and text input styling
- Update search_user view to handle query parameter and render user results
- Register fancy-button and generic-form scripts in app.html template
- Modify fancy-button to support form submission via 'submit' url attribute

src/snek/templates/app.html

@@ -6,7 +6,9 @@
   <title>Snek</title>
   <style>{{highlight_styles}}</style>
   <script src="/push.js"></script>
+  <script src="/fancy-button.js"></script>
   <script src="/upload-button.js"></script>
+  <script src="/generic-form.js"></script>
   <script src="/html-frame.js"></script>
   <script src="/schedule.js"></script>
   <script src="/app.js"></script>