fix(routing): canonicalize board page 1 routes instead of not-found

Board URLs ending in /1 now redirect to the canonical page-1 path while
preserving search, hash, and settings suffixes.

src/__tests__/app.test.tsx

@@ -431,11 +431,16 @@ describe('App', () => {
     expect(container.querySelector('[data-testid="board-blotter"]')).toBeTruthy();
   });
 
-  it('redirects board page 1 feeds to not-found', async () => {
-    await renderApp('/mu/1');
+  it.each([
+    ['/mu/1', '/mu'],
+    ['/mu/1?focus=1', '/mu?focus=1'],
+    ['/mu/1/settings?focus=1', '/mu/settings?focus=1'],
+  ])('canonicalizes board page 1 route %s to %s', async (initialEntry, expectedLocation) => {
+    await renderApp(initialEntry);
 
-    expect(latestLocation).toBe('/not-found');
-    expect(container.querySelector('[data-testid="not-found-view"]')).toBeTruthy();
+    expect(latestLocation).toBe(expectedLocation);
+    expect(container.querySelector('[data-testid="board-header"]')).toBeTruthy();
+    expect(container.querySelector('[data-testid="not-found-view"]')).toBeNull();
   });
 
   it('redirects flash board catalog routes to not-found', async () => {

src/app.tsx

@@ -72,10 +72,12 @@ preloadReplyModal();
 
 const getPostFormRouteKeyPath = (pathname: string) => pathname.replace(/\/settings$/, '').replace(/\/$/, '');
 
+const getPageOneCanonicalPath = (boardIdentifier: string, pathname: string) => `/${boardIdentifier}${pathname.endsWith('/settings') ? '/settings' : ''}`;
+
 const BoardLayout = () => {
   const params = useParams();
   const { accountCommentIndex, boardIdentifier, pageNumber } = params;
-  const { pathname, search } = useLocation();
+  const { pathname, search, hash } = useLocation();
   const isMobile = useIsMobile();
   const isInAllView = isAllView(pathname);
   const isInSubscriptionsView = isSubscriptionsView(pathname, useParams());
@@ -113,8 +115,8 @@ const BoardLayout = () => {
   // force rerender of post form when navigating between pages, except when opening settings modal in current view
   const key = `${communityAddress}-${getPostFormRouteKeyPath(pathname)}`;
 
-  if (pageNumber === '1') {
-    return <Navigate to='/not-found' replace />;
+  if (pageNumber === '1' && boardIdentifier) {
+    return <Navigate to={{ pathname: getPageOneCanonicalPath(boardIdentifier, pathname), search, hash }} replace />;
   }
 
   if (isCatalogView(pathname, params) && isFlashBoardRoute(boardIdentifier, directories)) {