fix(backend): ensure deps are coupled (#9649)

* fix(backend): ensure deps are coupled

* bump deps

* more constraints

* run dep resolver

* expand resolve even more

* lower lxml / xmlsec

* lower allauth

docs/requirements.in

@@ -1,3 +1,4 @@
+-c ../src/backend/requirements.txt
 mkdocs==1.6.1
 mkdocs-macros-plugin>=0.7,<2.0
 mkdocs-material>=9.0,<10.0