feat: dark-tech UI redesign + markdown patch cards

Redesign the frontend with a dark-tech theme: add Tailwind + PostCSS,
design tokens, and shadcn-style primitives (Button/Card/Input/Dialog/
DropdownMenu/Tabs/ScrollArea/etc.); restyle the app shell, navigation,
sidebar tree, content view, markdown rendering, editors, modals and
settings panels. Behavior/props unchanged; Font Awesome replaced with
lucide-react.

Add the patch cards feature UI: patch-queries hooks and a PatchCards
component rendered below the markdown body, with an Add Patch button
and create/edit dialog.

Fix tree expandability: folders with an index page now expand on name
click (and navigate), and the chevron+folder icon is one larger toggle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/KeycloakCallbacks/Callback.js

@@ -1,6 +1,7 @@
 import React, {useContext, useEffect} from "react";
 import { UserManager } from "oidc-client-ts";
 import {ConfigContext} from "../../ConfigProvider";
+import { Spinner } from "../ui/misc";
 
 
 const Callback = () => {
@@ -13,7 +14,11 @@ const Callback = () => {
             });
     }, []);
 
-    return <div>Logging in...</div>;
+    return (
+        <div className="flex min-h-screen items-center justify-center">
+            <Spinner label="Logging in" />
+        </div>
+    );
 };
 
 export default Callback;