Remove all Django-specific naming from mizan-react

Renamed:
  DjangoError         → MizanError
  DjangoHTTPClient    → MizanHTTPClient
  DjangoFormState     → MizanFormState
  DjangoFormsetState  → MizanFormsetState
  createDjangoCSRClient → createMizanCSRClient
  createDjangoSSRClient → createMizanSSRClient
  ensureDjangoSession → ensureMizanSession
  useDjangoCSRClient  → useMizanCSRClient
  TDjangoMessage      → TServerMessage

Made CSRF configurable:
  configureCsrf(cookieName, headerName) — defaults to Django
  conventions but works with any backend that uses CSRF tokens.
  Cookie name and header name are no longer hardcoded.

All old names preserved as deprecated aliases in index.ts exports
for backwards compatibility.

Removed dead RouterAdapter re-export (file moved to legacy/).

33 React tests pass.

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

packages/mizan-react/src/utils.ts

@@ -2,9 +2,28 @@
  * Shared utilities used across mizan-react.
  */
 
+/** Default CSRF cookie name. Configurable via MizanProvider. */
+let _csrfCookieName = 'csrftoken'
+
+/** Default CSRF header name. Configurable via MizanProvider. */
+let _csrfHeaderName = 'X-CSRFToken'
+
+export function configureCsrf(cookieName: string, headerName: string): void {
+    _csrfCookieName = cookieName
+    _csrfHeaderName = headerName
+}
+
+export function getCsrfCookieName(): string {
+    return _csrfCookieName
+}
+
+export function getCsrfHeaderName(): string {
+    return _csrfHeaderName
+}
+
 /** Extract CSRF token from cookies. Returns null during SSR. */
 export function getCSRFToken(): string | null {
     if (typeof document === 'undefined') return null
-    const match = document.cookie.match(/csrftoken=([^;]+)/)
+    const match = document.cookie.match(new RegExp(`${_csrfCookieName}=([^;]+)`))
     return match?.[1] ?? null
 }