[Feature] Make ApiConfig integration slots optional

[lukasz-hycom]

Is your feature request related to a problem? Please describe.
ApiConfig in packages/framework/src/api-config.ts requires all 18 integration slots. A simple project that only uses CMS + Tickets + Auth still needs to provide stub configs for Orders, Carts, Products, Checkout, Payments, etc. This creates unnecessary boilerplate and makes onboarding harder for projects with limited integration needs.

Describe the solution you'd like
Make non-core integrations optional:

export interface ApiConfig {
    integrations: {
        // Core — always needed
        cms: IntegrationSlot<CMS.Service, CMS.Controller>;
        auth: IntegrationSlot<Auth.Service>;

        // Optional — provide only what you use
        tickets?: IntegrationSlot<Tickets.Service, Tickets.Controller>;
        articles?: IntegrationSlot<Articles.Service, Articles.Controller>;
        orders?: IntegrationSlot<Orders.Service, Orders.Controller>;
        // ...
    };
}

The framework modules that use optional integrations would check for existence and skip registration gracefully.

Additional context (if applicable)

• Key file: packages/framework/src/api-config.ts

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