fix(gateway): remove re-introduced auth.mode=none pairing bypass

The revert of #43478 (commit 39b4185d0b) was silently undone by
3704293e6f which was based on a branch that included the original
change. This removes the auth.mode=none skipPairing condition again.

The blanket skip was too broad - it disabled pairing for ALL websocket
clients, not just Control UI behind reverse proxies.

src/gateway/server/ws-connection/message-handler.ts

@@ -674,18 +674,14 @@ export function attachGatewayWsMessageHandler(params: {
           authOk,
           authMethod,
         });
-        // auth.mode=none disables all authentication — device pairing is an
-        // auth mechanism and must also be skipped when the operator opted out.
         const skipPairing =
-          resolvedAuth.mode === "none" ||
           shouldSkipBackendSelfPairing({
             connectParams,
             isLocalClient,
             hasBrowserOriginHeader,
             sharedAuthOk,
             authMethod,
-          }) ||
-          shouldSkipControlUiPairing(controlUiAuthPolicy, role, trustedProxyAuthOk);
+          }) || shouldSkipControlUiPairing(controlUiAuthPolicy, role, trustedProxyAuthOk);
         if (device && devicePublicKey && !skipPairing) {
           const formatAuditList = (items: string[] | undefined): string => {
             if (!items || items.length === 0) {