feat(review): review queue for leads + manual reviewer reassignment

Leads get the same two-queue view operators already have: 'Available
to Review' (pending reviews currently assigned to a peer lead) and
'My Assigned Reviews' (assigned to me), replacing the old single
'My Reviews' toggle. Since the load-balanced auto-assignment always
picks a reviewer immediately, 'available' means peer-assigned reviews
a lead could pick up if the assignee can't get to them, not unclaimed
ones (there aren't any).

POST /tests/{id}/assign now also accepts red_reviewer_assignee /
blue_reviewer_assignee, validated against the matching lead role and
synced to Jira the same way operator assignment already is. The
AssigneeControl UI gained a 'reviewer' kind (leads-only picker) shown
on the test detail header while a test sits in red_review/blue_review
— this also fixes the reviewer assignment being invisible in Aegis
even though it was already being pushed to Jira correctly.

backend/tests/test_assign_operators.py

@@ -148,3 +148,77 @@ def test_assigning_operator_syncs_to_jira(client, db, red_lead_headers, red_lead
     mock_push.assert_called_once()
     assert captured["test_id"] == test.id
     assert captured["assignee_id"] == red_tech_user.id
+
+
+def _make_second_red_lead(db):
+    from app.auth import hash_password
+    from app.models.user import User
+    u = User(
+        username="redlead2", email="redlead2@test.com",
+        hashed_password=hash_password("x"), role="red_lead", is_active=True,
+        must_change_password=False,
+    )
+    db.add(u)
+    db.commit()
+    db.refresh(u)
+    return u
+
+
+def test_lead_can_reassign_red_reviewer_to_peer(client, db, red_lead_headers, red_lead_user):
+    """A lead can hand a review off to a peer lead — e.g. if the currently
+    assigned reviewer can't get to it."""
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, red_lead_user.id)
+    peer = _make_second_red_lead(db)
+    test.red_reviewer_assignee = red_lead_user.id
+    db.commit()
+
+    resp = client.post(
+        f"/api/v1/tests/{test.id}/assign",
+        json={"red_reviewer_assignee": str(peer.id)},
+        headers=red_lead_headers,
+    )
+    assert resp.status_code == 200, resp.text
+    assert resp.json()["red_reviewer_assignee"] == str(peer.id)
+
+    db.refresh(test)
+    assert test.red_reviewer_assignee == peer.id
+
+
+def test_reviewer_reassign_rejects_non_lead(client, db, red_lead_headers, red_lead_user, red_tech_user):
+    """Only a red_lead can be the red reviewer — a red_tech is not eligible."""
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, red_lead_user.id)
+
+    resp = client.post(
+        f"/api/v1/tests/{test.id}/assign",
+        json={"red_reviewer_assignee": str(red_tech_user.id)},
+        headers=red_lead_headers,
+    )
+    assert resp.status_code == 400
+
+
+def test_reviewer_reassign_rejects_wrong_side(client, db, red_lead_headers, red_lead_user, blue_lead_user):
+    """A blue_lead can't be set as the red reviewer."""
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, red_lead_user.id)
+
+    resp = client.post(
+        f"/api/v1/tests/{test.id}/assign",
+        json={"red_reviewer_assignee": str(blue_lead_user.id)},
+        headers=red_lead_headers,
+    )
+    assert resp.status_code == 400
+
+
+def test_manager_can_reassign_blue_reviewer(client, db, manager_headers, manager_user, blue_lead_user):
+    technique = _seed_technique(db)
+    test = _seed_test(db, technique, manager_user.id)
+
+    resp = client.post(
+        f"/api/v1/tests/{test.id}/assign",
+        json={"blue_reviewer_assignee": str(blue_lead_user.id)},
+        headers=manager_headers,
+    )
+    assert resp.status_code == 200, resp.text
+    assert resp.json()["blue_reviewer_assignee"] == str(blue_lead_user.id)