fix(permissions): expose GET /api/acks, /api/ta1-acks, /api/277ca-acks

The PERMISSIONS matrix only listed the POST /api/acks entry (parse-999
ingest). The GET list + detail endpoints for 999 / TA1 / 277CA acks
were missing, so the matrix_gate (default-deny) returned 403 to every
authenticated role, breaking the 999 ACKs / TA1 / 277CA inbox pages.

Add the three GET entries as ALL_ROLES — they're read-only metadata
surfaces that every authenticated operator needs to see. Add a
regression test that logs in as admin via the public route and
exercises the matrix; the existing test_existing_endpoints_require_auth
suite only checks the unauthenticated 401 path, which is why this slipped
through.

Fixes the live-verification 'Couldn't load ACKs from the backend /
forbidden' error reported against the UI.

backend/src/cyclone/auth/permissions.py

@@ -44,6 +44,9 @@ PERMISSIONS: dict[tuple[str, str], set[Role]] = {
     ("GET", "/api/inbox/export.csv"): ALL_ROLES,
     ("GET", "/api/reconcile"): ALL_ROLES,
     ("GET", "/api/reconciliation"): ALL_ROLES,
+    ("GET", "/api/acks"): ALL_ROLES,
+    ("GET", "/api/ta1-acks"): ALL_ROLES,
+    ("GET", "/api/277ca-acks"): ALL_ROLES,
     ("GET", "/api/audit-log"): ADMIN_ONLY,
 
     # Write endpoints (admin + user, no viewer).

backend/tests/test_ack_endpoints_authenticated.py

@@ -0,0 +1,71 @@
+"""Regression: GET /api/acks, /api/ta1-acks, /api/277ca-acks must be reachable
+for an authenticated admin. The PERMISSIONS matrix only listed the
+``POST /api/acks`` (parse-999) entry, so the GET list/detail endpoints
+returned 403 to admins and broke the Inbox / 999 ACKs pages on the UI.
+
+This test exercises the matrix via the public login route — not by
+flipping ``AUTH_DISABLED`` — so a missing ``("GET", "/api/<kind>-acks"):
+ALL_ROLES`` entry would surface as 403.
+"""
+
+from __future__ import annotations
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy import delete
+
+from cyclone.api import app
+from cyclone.auth import users
+from cyclone.db import Session as DbSession
+from cyclone.db import SessionLocal, User
+
+
+@pytest.fixture(autouse=True)
+def _clear(monkeypatch):
+    monkeypatch.setattr("cyclone.auth.deps.AUTH_DISABLED", False)
+    with SessionLocal()() as db:
+        db.execute(delete(DbSession))
+        db.execute(delete(User))
+        db.commit()
+    yield
+    with SessionLocal()() as db:
+        db.execute(delete(DbSession))
+        db.execute(delete(User))
+        db.commit()
+
+
+@pytest.fixture
+def client():
+    return TestClient(app)
+
+
+@pytest.fixture
+def admin_client(client):
+    with SessionLocal()() as db:
+        users.create(db, username="admin", password="adminpassword1", role="admin")
+    resp = client.post(
+        "/api/auth/login",
+        json={"username": "admin", "password": "adminpassword1"},
+    )
+    assert resp.status_code == 200
+    return client
+
+
+@pytest.mark.parametrize("path", [
+    "/api/acks",
+    "/api/acks/0",
+    "/api/ta1-acks",
+    "/api/ta1-acks/0",
+    "/api/277ca-acks",
+    "/api/277ca-acks/0",
+])
+def test_admin_can_list_and_detail_all_ack_kinds(admin_client, path):
+    resp = admin_client.get(path, headers={"Accept": "application/json"})
+    # 200 for the list endpoint (empty rows is fine), 404 for the detail
+    # of a non-existent id (the gate must let the request through).
+    assert resp.status_code in (200, 404), (
+        f"{path} returned {resp.status_code}: {resp.text}"
+    )
+    assert resp.status_code != 403, (
+        f"{path} returned 403 — PERMISSIONS matrix is missing a GET entry"
+    )