feat(core-trpc): scaffold tRPC client with React Query providers

- createTRPCContext + useTRPC hook for typed client access
- NextTrpcProvider with SSR-safe absolute URL resolution
- TanstackTrpcProvider for TanStack Start apps
- /api/trpc catch-all route handler in web-next
- Wire NextTrpcProvider into app providers
- Add @repo/core-trpc to transpilePackages

packages/core-trpc/src/index.ts

@@ -0,0 +1,3 @@
+export { useTRPC, TRPCProvider } from "./client";
+export { getQueryClient } from "./query-client";
+export type { AppRouter } from "@repo/core-api";