Add API Usage Tracking per Sub-Client (API Key per Client)

Implement a feature that allows tracking and managing API usage per sub-client for all Skulytics clients (AIO, Reusely, and R&A, etc)
Each client should be able to generate and use different API keys for their own sub-clients. This will allow us to:

• Track API usage individually for each sub-client.

• Set usage limits or restrictions per sub-client if needed.

• Improve billing accuracy and monitoring across all client accounts.

Scope:
Applies to all main clients (AIO, Reusely, and R&A, etc) and their respective sub-clients.