feat: Add X-Apify-Request-Origin: MCP header to API requests

[RobertCrupa]

Summary

• Adds X-Apify-Request-Origin: MCP header to all outbound Apify API requests via a new addRequestOrigin interceptor in ApifyClient
• Keeps existing Origin/mcp-server token in User-Agent unchanged
• All 13 ApifyClient instantiation sites pick up the new header automatically — no call-site changes needed

New Request Header

I cut out the auth ;)

Closes #832

[MQ37]

Thx bro!

[jirispilka]

Nice!

@gippy this will be deployed tomorrow. Do you need anything else from us? Verification?

Btw, pre-existing issue:

Two functions to update headers

        const { paymentHeaders, ...clientOptions } = options;
        const requestInterceptors = [addUserAgent, addRequestOrigin];

directly followed with another update:

        if (paymentHeaders && Object.keys(paymentHeaders).length > 0) {
            requestInterceptors.push((config) => {
                const updatedConfig = { ...config };
                updatedConfig.headers = updatedConfig.headers ?? {};
                Object.assign(updatedConfig.headers, paymentHeaders);
                return updatedConfig;
            });
        }

This should be consistent, worth of a separate PR though.

[jirispilka]

@RobertCrupa this can be merged.
I was first told by Jarda not to merge it and then he said it is ok :)