fix(mcp): normalize empty-string oauthClientId at route boundary

Orchestration already converts falsy → null via `|| null` (server-lifecycle.ts),
so the DB was never receiving an empty string. Tightening the route layer to
match the same convention keeps the boundary contract consistent and avoids
relying on downstream normalization.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: waleedlatif1

apps/sim/app/api/mcp/servers/[id]/route.ts

@@ -60,7 +60,7 @@ export const PATCH = withRouteHandler(
           retries: body.retries,
           enabled: body.enabled,
           authType: body.authType,
-          oauthClientId: body.oauthClientId ?? null,
+          oauthClientId: body.oauthClientId || null,
           oauthClientIdProvided: body.oauthClientId !== undefined,
           oauthClientSecret: body.oauthClientSecret,
           oauthClientSecretProvided: body.oauthClientSecret !== undefined,

apps/sim/app/api/mcp/servers/route.ts

@@ -95,7 +95,7 @@ export const POST = withRouteHandler(
           enabled: body.enabled,
           source,
           authType: body.authType,
-          oauthClientId: body.oauthClientId ?? null,
+          oauthClientId: body.oauthClientId || null,
           oauthClientIdProvided: body.oauthClientId !== undefined,
           oauthClientSecret: body.oauthClientSecret,
           oauthClientSecretProvided: body.oauthClientSecret !== undefined,