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/ConfigContext.tsx

@@ -0,0 +1,29 @@
+'use client'
+
+import { createContext, ReactNode, useContext, useMemo } from 'react'
+import { AllauthConfig, defaultConfig, createAllauthConfig } from '../config'
+
+const Context = createContext<AllauthConfig>(defaultConfig)
+
+interface ConfigContextProps {
+    children: ReactNode
+    config?: Partial<AllauthConfig>
+}
+
+export function ConfigContext({ children, config }: ConfigContextProps) {
+    // Memoize the merged config to prevent creating new objects on every render
+    const mergedConfig = useMemo(
+        () => config ? createAllauthConfig(config) : defaultConfig,
+        [config]
+    )
+
+    return (
+        <Context value={mergedConfig}>
+            {children}
+        </Context>
+    )
+}
+
+export function useAllauthConfig(): AllauthConfig {
+    return useContext(Context)
+}