Surface redacted directory bind failures before native onboarding

Map uncaught HTTPError from LLDAP login to a structured
dependency_unavailable response, add /readyz as the provisioner-to-directory
preflight, keep /healthz as process liveness, and run the contract in CI.
Auth rejection is not retried during cooldown.

NK-WP-0036-T05 remains in progress until the immutable image is published,
pinned with /readyz, and one native login/create/password-setup journey is
verified.

Assistant: grok
Assistant-Session: 01a09dc6-3f0e-78f1-a884-c8c703c24ddf

.forgejo/workflows/identity-journeys.yaml

@@ -10,7 +10,7 @@ jobs:
     container:
       image: python:3.12-slim@sha256:d764629ce0ddd8c71fd371e9901efb324a95789d2315a47db7e4d27e78f1b0e9
     steps:
-      - name: Test the exact commit
+      - name: Run provider and directory-contract tests
         run: |
           set -eu
           mkdir -p identity-source