Add x-vercel-protection-bypass to the allowed headers for MCP servers

### Problem Statement

I'm trying to test a preview MCP server that is deployed to Vercel, but I have [Deployment Protection](https://vercel.com/docs/deployment-protection/methods-to-bypass-deployment-protection/protection-bypass-automation) enabled, so I need to pass x-vercel-protection-bypass.

### Proposed Solution

Add x-vercel-protection-bypass to the whitelist.

### Alternatives Considered

_No response_

### Area

MCP Connector (adding/managing servers)

### Priority

Critical - Blocking my MCP server development

### Additional Context

_No response_

The issue names no file or test; start by locating the MCP Connector code that defines the allowed request-header whitelist and its existing header-validation tests. Add x-vercel-protection-bypass to that whitelist, then run the relevant test suite and confirm the header is accepted.

Scritto dal modello di indicizzazione a partire dal testo della issue.