Refactor the Endpoint logic

Currently Endpoint_List and Endpoints_Repository are re-declared in each feature they are used (AI, Task List, Dashboard). We should isolate them and re-use when needed.
Moreover, we need to introduce specific Endpoint_Interface implementations for the the consent, Free Sparks and generator routes so that they can be gathered by the Endpoint_Repository and exposed to the frontend like we do for the Dashboard. This will avoid hard-coding the endpoints in the frontend code.
These changes were introduced in the commits from 4159e7f847dec4001399b21f13968857e5b06ddb to 8960abd0a92dd70ba16b8b26f799c41552ba3d66, part of this now-closed PR

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