chore(slice-3): version 0.3, README status, label-input association fix (a11y §6.6)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/package.json

@@ -1,7 +1,7 @@
 {
   "name": "wiggleverse-ecomm-frontend",
   "private": true,
-  "version": "0.2.0",
+  "version": "0.3.0",
   "type": "module",
   "scripts": {
     "dev": "vite",

frontend/src/ui/kit.tsx

@@ -1,6 +1,7 @@
 // The ecomm UI kit — React faces of the app.css primitives, matching the Claude Design
 // export (ui/designs/ecomm-login-and-create-storefront-designs, hf-kit). Presentation
 // only: no business rules live here (§6.2 — the SPA renders what the BFF returns).
+import { useId } from "react";
 import type { ReactNode } from "react";
 
 export function Screen({
@@ -110,13 +111,15 @@ export function Field({
   helper?: string;
   inputProps: React.InputHTMLAttributes<HTMLInputElement>;
 }) {
+  const id = useId();
   return (
     <div className="field">
-      <label className="field__label">
+      <label className="field__label" htmlFor={id}>
         <span>{label}</span>
         {optional && <span className="field__optional">optional</span>}
       </label>
       <input
+        id={id}
         className={`field__input${error ? " field__input--error" : ""}`}
         aria-invalid={!!error}
         {...inputProps}