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/components/views/SignupView.tsx

@@ -0,0 +1,42 @@
+'use client'
+
+import { useAuthContext } from '../../contexts/AuthContext'
+import { getAuthDetails } from '../../api'
+import { AuthDjangoForm } from '../AuthDjangoForm'
+
+interface SignupViewProps {
+    /** Called after successful signup */
+    onSuccess?: () => void
+    /** Called when user clicks "Already have an account? Sign in" */
+    onLoginClick?: () => void
+}
+
+export function SignupView({
+    onSuccess,
+    onLoginClick,
+}: SignupViewProps) {
+    const { refresh } = useAuthContext()
+
+    const handleSuccess = async () => {
+        const newAuth = await refresh()
+        const details = getAuthDetails(newAuth)
+
+        if (details.isAuthenticated) {
+            onSuccess?.()
+        }
+    }
+
+    const footerLinks: Array<{ label: string; onClick?: () => void }> = []
+
+    if (onLoginClick) {
+        footerLinks.push({ label: 'Already have an account? Sign in', onClick: onLoginClick })
+    }
+
+    return (
+        <AuthDjangoForm
+            formName="signup"
+            onSuccess={handleSuccess}
+            footerLinks={footerLinks}
+        />
+    )
+}