fix(web): refuse unauthenticated bind on non-loopback address (W5)

In open mode ([web.oidc] unset) the dashboard has no login. Binding a LAN/any address there would expose host-management unauthenticated, so ci web serve now aborts unless the bind host is loopback. Auth-configured deployments bind LAN as before.

tests/python/test_commands_web.py

@@ -148,3 +148,71 @@ def test_web_group_registered_on_root_cli() -> None:
 def test_config_import_does_not_require_web_extra() -> None:
     """``Config``/``load_config`` (imported lazily inside serve) is core, not [web]."""
     assert Config is not None
+
+
+# ── W5 security guard: no unauthenticated bind on a non-loopback address ──────
+
+
+def _cfg(*, oidc: bool, tmp: Path) -> Config:
+    from ci_orchestrator.config import (
+        BackendConfig,
+        Paths,
+        WebConfig,
+        WebOidcConfig,
+    )
+
+    web_oidc = (
+        WebOidcConfig(issuer="https://gitea.lan", client_id="cid", redirect_url="http://x/cb")
+        if oidc
+        else None
+    )
+    return Config(
+        paths=Paths(
+            root=tmp,
+            templates=tmp / "templates",
+            build_vms=tmp / "build-vms",
+            artifacts=tmp / "artifacts",
+            keys=tmp / "keys",
+        ),
+        backend=BackendConfig(),
+        web=WebConfig(oidc=web_oidc),
+    )
+
+
+@pytest.mark.parametrize("host", ["127.0.0.1", "::1", "localhost", ""])
+def test_is_loopback_true(host: str) -> None:
+    assert web_module._is_loopback(host) is True
+
+
+@pytest.mark.parametrize("host", ["192.168.1.50", "10.0.0.5", "0.0.0.0", "gitea.lan"])
+def test_is_loopback_false(host: str) -> None:
+    assert web_module._is_loopback(host) is False
+
+
+def test_bind_guard_blocks_lan_bind_without_oidc(tmp_path: Path) -> None:
+    err = web_module._bind_guard_error("192.168.1.50", _cfg(oidc=False, tmp=tmp_path))
+    assert err is not None
+    assert "refusing to bind" in err
+
+
+def test_bind_guard_allows_lan_bind_with_oidc(tmp_path: Path) -> None:
+    assert web_module._bind_guard_error("192.168.1.50", _cfg(oidc=True, tmp=tmp_path)) is None
+
+
+def test_bind_guard_allows_loopback_without_oidc(tmp_path: Path) -> None:
+    assert web_module._bind_guard_error("127.0.0.1", _cfg(oidc=False, tmp=tmp_path)) is None
+
+
+def test_web_serve_refuses_lan_bind_without_auth(monkeypatch: pytest.MonkeyPatch) -> None:
+    """End-to-end: ``serve`` aborts (and never starts uvicorn) on an unsafe bind.
+
+    The autouse fixture points config at an empty tmp dir → ``web.oidc`` is
+    ``None`` (open mode), so a non-loopback ``--host`` must be refused.
+    """
+    calls = _install_fake_uvicorn(monkeypatch)
+
+    result = CliRunner().invoke(cli, ["web", "serve", "--host", "10.0.0.5", "--port", "8800"])
+
+    assert result.exit_code != 0
+    assert "refusing to bind" in result.output
+    assert calls == [], "uvicorn.run must never be called on a refused bind"