feat(web): /fields two-pane screen (grouped list + create form) + nav (no stubs left)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/app.tsx

@@ -22,6 +22,10 @@ const ObjectEditForm = lazy(() =>
   import("./objects/object-edit-form").then((m) => ({ default: m.ObjectEditForm })),
 );
 
+const FieldsPage = lazy(() =>
+  import("./fields/fields-page").then((m) => ({ default: m.FieldsPage })),
+);
+
 function FormFallback() {
   return <div role="status" className="p-4 text-sm text-neutral-400">Loading…</div>;
 }
@@ -63,6 +67,14 @@ export function App() {
             </Route>
             <Route path="/authorities" element={<Navigate to="/authorities/person" replace />} />
             <Route path="/authorities/:kind" element={<AuthoritiesPage />} />
+            <Route
+              path="/fields"
+              element={
+                <Suspense fallback={<FormFallback />}>
+                  <FieldsPage />
+                </Suspense>
+              }
+            />
             <Route path="/" element={<Navigate to="/objects" replace />} />
           </Route>
         </Route>