Expose AISHub as an optional ships-layer backup when AISStream is silent.

Wire AISHUB_USERNAME into API Keys and onboarding, and surface backup status on the AIS outage banner so operators can keep vessel coverage without changing the AISStream proxy.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/tests/test_aishub_api_settings.py

@@ -0,0 +1,9 @@
+from services.api_settings import ALLOWED_ENV_KEYS, API_REGISTRY
+
+
+def test_aishub_username_is_in_api_registry():
+    entry = next((item for item in API_REGISTRY if item.get("env_key") == "AISHUB_USERNAME"), None)
+    assert entry is not None
+    assert entry["category"] == "Maritime"
+    assert entry["required"] is False
+    assert "AISHUB_USERNAME" in ALLOWED_ENV_KEYS