feat(sp40): edifabric.api_key secret wiring + dev fixture

backend/tests/fixtures/edifabric_api_key.txt

@@ -0,0 +1,16 @@
+# SP40: dev-only public eval key for the EdiNation / Edifabric
+# /v2/x12/validate reference parser. This key has hit the public
+# evaluation docs and is documented as a "developer API" provisional
+# key — fine for local CI / smoke tests, never ship to production.
+#
+# Production deployments MUST override via the secrets layer:
+#
+#   cyclone secrets set edifabric.api_key <paid-tier-key>
+#   # or
+#   export CYCLONE_EDIFABRIC_API_KEY_FILE=/path/to/paid-key.txt
+#
+# The fixture is referenced by name so the URL-reminder route survives
+# refactors; the actual key isn't sent over the wire because every
+# test patches edifabric.set_transport_factory() and secrets.get_secret
+# before invoke.
+3ecf6b1c5cf34bd797a5f4c57951a1cf