refactor: overhaul UI for streamlined user experience

Redesign navigation, home overview, user portrait, and valuation pages
with improved functionality and responsive design.

Co-authored-by: null <4804959+fnvtk@users.noreply.github.com>

app/api-interface/loading.tsx

@@ -0,0 +1,3 @@
+export default function Loading() {
+  return null
+}