feat(web): add TanStack Query infrastructure (Phase 0)

- Install @tanstack/react-query v5 + devtools
- Create core/query-client.ts with WS-optimized defaults (staleTime: Infinity)
- Create QueryProvider and wire into root layout
- Add @core/* path alias to tsconfig + vitest
- Add useWorkspaceId() bridge hook for query key scoping

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/core/query-client.ts

@@ -0,0 +1,18 @@
+import { QueryClient } from "@tanstack/react-query";
+
+export function createQueryClient(): QueryClient {
+  return new QueryClient({
+    defaultOptions: {
+      queries: {
+        staleTime: Infinity,
+        gcTime: 10 * 60 * 1000, // 10 minutes
+        refetchOnWindowFocus: false,
+        refetchOnReconnect: false,
+        retry: 1,
+      },
+      mutations: {
+        retry: false,
+      },
+    },
+  });
+}