[Deferred] Rate limiting for MCPRemoteProxy

[jerm-dro]

User Story

As a cluster admin,
I want rate limiting on MCPRemoteProxy,
so that proxied remote MCP traffic is also protected.

Context

Deferred — not part of the initial implementation. Created for visibility.

MCPRemoteProxy shares the same MiddlewareFactory registry as MCPServer, so integration should be straightforward. See THV-0057.

Acceptance Criteria

• rateLimiting on MCPRemoteProxy spec
• Same middleware and config as MCPServer

Dependencies

• STORY-001, STORY-002 (core rate limit infrastructure)