Add request timeouts to federation HTTP calls

Description

Federation HTTP requests in FederationRequestService.makeSignedRequest() currently lack timeout handling, which can cause requests to hang indefinitely on network issues.

Context

The @hs/core fetch implementation doesn't include built-in timeout support. This was identified during review of PR #191.

Proposed Solution

Add configurable timeout support using one of these approaches:

1. Use AbortController with setTimeout to cancel long-running requests
2. Extend @hs/core fetch to accept timeoutMs or signal parameters
3. Add a configurable timeout (e.g., FEDERATION_REQUEST_TIMEOUT_MS) with reasonable default (~15s)

Files Affected

• packages/federation-sdk/src/services/federation-request.service.ts
• Potentially @hs/core fetch implementation

References

• Original PR: https://github.com/RocketChat/homeserver/pull/191
• Comment: https://github.com/RocketChat/homeserver/pull/191#discussion_r2351945893

/cc @debdutdeb