fix(web): work around TanStack Router hash history index route bug

TanStack Router with hash history doesn't match the index route for root
path "/" - it falls through to _not-found. This is a known issue:
TanStack/router#5528

Workaround:
- Add redirect script in index.html to ensure "/" redirects to "/#/"
- Detect root path in _not-found.tsx and render HomePage instead of 404
- Simplify index.tsx lazy import pattern for consistency

Author: Mearman

apps/web/index.html

@@ -20,6 +20,15 @@
     <meta property="twitter:title" content="BibGraph - Explore Academic Research" />
     <meta property="twitter:description" content="Explore academic research data from OpenAlex, visualize citation networks, and discover research relationships across works, authors, institutions, and more." />
 
+    <script>
+      // Redirect to hash-based home route if no hash is present
+      // This ensures users landing on "/" get properly routed to "/#/"
+      (function() {
+        if (!window.location.hash || window.location.hash === '#') {
+          window.location.replace(window.location.pathname + '#/');
+        }
+      })();
+    </script>
     <script>
       // Prevent flash of wrong theme by setting color scheme before React loads
       (function() {

apps/web/src/routes/_not-found.tsx

@@ -1,10 +1,29 @@
 import { Alert, Button,Container, Group, Stack, Text, Title } from "@mantine/core";
 import { IconHome, IconSearch } from "@tabler/icons-react";
-import { createFileRoute } from "@tanstack/react-router";
+import { createFileRoute, useLocation } from "@tanstack/react-router";
+import { lazy, Suspense } from "react";
 
 import { ICON_SIZE } from "@/config/style-constants";
 
+// Lazy load HomePage for when we need to render it as fallback for root path
+// This works around a TanStack Router bug where the index route isn't matched
+const HomePage = lazy(() => import("./index.lazy"));
+
 const NotFoundRoute = () => {
+  const location = useLocation();
+
+  // Workaround for TanStack Router bug: index route not matching root path
+  // See: https://github.com/TanStack/router/issues/5528
+  if (location.pathname === "/") {
+    console.log("[NOT FOUND ROUTE] Root path detected, rendering HomePage as workaround");
+    return (
+      <Suspense fallback={<div style={{ padding: "40px", textAlign: "center" }}>Loading...</div>}>
+        <HomePage />
+      </Suspense>
+    );
+  }
+
+  console.log("[NOT FOUND ROUTE] Rendering 404 component");
   return (
     <Container size="md" py="xl">
       <Stack gap="md" align="center">

apps/web/src/routes/index.tsx

@@ -3,14 +3,12 @@ import { lazy } from "react";
 
 import { LazyRoute } from "@/components/routing/LazyRoute";
 
-const IndexRoute = lazy(() =>
-  import("./index.lazy").then((m) => ({ default: m.default })),
-);
+const HomePage = lazy(() => import("./index.lazy"));
 
 export const Route = createFileRoute("/")({
   component: () => (
     <LazyRoute>
-      <IndexRoute />
+      <HomePage />
     </LazyRoute>
   ),
 });