Polish: UI theme colors, onboarding dismiss, Export button in sidebar (#270)

* Light mode style fixes

* Fix dismissing onboarding for nested routes

* Refactor: move export button to  user side panel

* Refactor: add project data to modeling page loader

* Add new ProjectSidebarMenu

* Convert AppHeader to use ProjectSidebarMenu

* Move ExportButton to ProjectSidebarMenu

* Fix: hide default dir setting in Web

* Add DownloadAppBanner when in Prod

* Add unit tests to ProjectSidebarMenu

* Tiny CSS rounding tweak to sidebars

* Fix formatting in unit tests

* Update icons and logos to use full-color Kitt

* Fix: dim UI on camera drag, not click

src/components/DownloadAppBanner.tsx

@@ -0,0 +1,29 @@
+const DownloadAppBanner = () => {
+  return (
+    <div className="fixed inset-0 top-auto z-50 bg-warn-20 text-warn-80 px-8 py-4">
+      <div className="max-w-3xl mx-auto">
+        <h2 className="text-xl font-bold mb-4">
+          KittyCAD Modeling App is better as a desktop app!
+        </h2>
+        <p>
+          The browser version of the app only saves your data temporarily in{' '}
+          <code className="text-base inline-block px-0.5 bg-warn-30/50 rounded">
+            localStorage
+          </code>
+          , and isn't backed up anywhere! Visit{' '}
+          <a
+            href="https://github.com/KittyCAD/modeling-app/releases"
+            rel="noopener noreferrer"
+            target="_blank"
+            className="text-warn-80 dark:text-warn-80 dark:hover:text-warn-70 underline"
+          >
+            our GitHub repository
+          </a>{' '}
+          to download the app for the best experience.
+        </p>
+      </div>
+    </div>
+  )
+}
+
+export default DownloadAppBanner