Chore: anchor admin url pattern (#14316)

src/paperless/urls.py

@@ -300,7 +300,7 @@ urlpatterns = [
     ),
     re_path(r"^share/(?P<slug>\w+)/?$", SharedLinkView.as_view()),
     re_path(r"^favicon.ico$", FaviconView.as_view(), name="favicon"),
-    re_path(r"admin/", admin.site.urls),
+    re_path(r"^admin/", admin.site.urls),
     re_path(
         r"^fetch/",
         include(