Add NotFound page with picture

- Create NotFound component that displays not-found.png
- Add SCSS styles for the NotFound page
- Update App.jsx to show NotFound page for invalid routes instead of redirecting

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

src/styles/components/NotFound.module.scss

@@ -0,0 +1,39 @@
+@use '../variables' as *;
+
+.notFound {
+  padding: $space-24 $space-6;
+  min-height: 70vh;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.inner {
+  max-width: $max-width;
+  margin: 0 auto;
+  text-align: center;
+}
+
+.imageContainer {
+  margin-bottom: $space-8;
+}
+
+.image {
+  max-width: 100%;
+  height: auto;
+  border-radius: $radius-lg;
+  box-shadow: 0 0 30px rgb(var(--color-primary-mid) / 0.2);
+}
+
+.title {
+  font-size: $text-4xl;
+  font-weight: 700;
+  color: $color-text;
+  margin-bottom: $space-4;
+}
+
+.message {
+  font-size: $text-lg;
+  color: $color-text-muted;
+  line-height: 1.6;
+}