Move allauth + auth UI to legacy/

allauth/ (44 files) is a django-allauth React UI — a separate concern
from the Mizan protocol. Moved to legacy/ pending extraction into a
standalone mizan-django-allauth package.

Also moved to legacy/:
- client/AuthContext.tsx — generic auth state from /me endpoint
- client/RouterContext.tsx — framework-agnostic router adapter
- client/routing.tsx — UserRoute/StaffRoute/AnonymousRoute guards
- client/nextjs.tsx — Next.js router adapter for auth

These are auth UI infrastructure, not Mizan protocol. The Mizan core
only needs JWT for auth header selection (jwt/ stays — MizanProvider
depends on useJWT() to decide between Bearer and session auth).

Cleaned up re-exports in client/react.ts and vitest aliases.

33 React tests pass.

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

legacy/allauth/contexts/StylesContext.tsx

@@ -0,0 +1,49 @@
+'use client'
+
+import { createContext, useContext, ReactNode } from 'react'
+import { AuthClassNames, emptyClassNames } from '../styles/types'
+
+const Context = createContext<AuthClassNames>(emptyClassNames)
+
+interface StylesContextProps {
+    children: ReactNode
+    classNames?: AuthClassNames
+}
+
+export function StylesContext({ children, classNames }: StylesContextProps) {
+    return (
+        <Context value={classNames ?? emptyClassNames}>
+            {children}
+        </Context>
+    )
+}
+
+/**
+ * Hook to access auth component class names.
+ *
+ * Returns the class names provided to AllauthProvider, or empty strings if none provided.
+ * Use this to style custom components consistently with the auth UI.
+ *
+ * @example
+ * ```tsx
+ * function MyAuthComponent() {
+ *     const styles = useStyles()
+ *     return (
+ *         <div className={styles.card}>
+ *             <h1 className={styles.title}>Custom Auth View</h1>
+ *         </div>
+ *     )
+ * }
+ * ```
+ */
+export function useStyles(): AuthClassNames {
+    return useContext(Context)
+}
+
+/**
+ * Utility to get a class name, returning empty string if undefined.
+ * Useful for conditional class application.
+ */
+export function cx(...classNames: (string | undefined | false | null)[]): string {
+    return classNames.filter(Boolean).join(' ')
+}