Register the Backend role authority boundary

Why: The focused authorization module introduces four intentional dependencies that the architecture ratchet must review explicitly.

Evidence: make test-boundaries passed with 89 recorded edges after the initial full make test stopped at the unregistered-edge gate.

Impact: Records only app/authz, authz/store, server/authz, and store/authz; no unrelated dependency edge is admitted.

Refs: Focused role and permission system task 8

policy/architecture-baseline.json

@@ -1,4 +1,5 @@
 [
+"backend/app backend/authz",
 "backend/app backend/blobstore",
 "backend/app backend/bus",
 "backend/app backend/cardsvc",
@@ -26,6 +27,7 @@
 "backend/app backend/surfacesvc",
 "backend/app backend/tools",
 "backend/app backend/workflow",
+"backend/authz backend/store",
 "backend/cardsvc backend/store",
 "backend/hostapi backend/store",
 "backend/pgbus backend/bus",
@@ -59,6 +61,7 @@
 "backend/runtime backend/squadadapter",
 "backend/runtime backend/wfcompile",
 "backend/runtime backend/workflow",
+"backend/server backend/authz",
 "backend/server backend/cardsvc",
 "backend/server backend/cmdbus",
 "backend/server backend/ingest",
@@ -77,6 +80,7 @@
 "backend/server backend/workflow",
 "backend/settings backend/store",
 "backend/squadadapter backend/quality",
+"backend/store backend/authz",
 "backend/store backend/blobstore",
 "backend/surfacesvc backend/store",
 "backend/tools backend/quality",