[BE][TechTix] Create new QuestionType Specific for PyCon

[ASPactores]

Extend the evaluation system to support PyCon-specific questions alongside existing generic event questions.

• Create PyconEvaluationQuestionType enum in model/evaluations/evaluations_constants.py.
• Update evaluation models to a union of both PyconEvaluationQuestionType and EvaluationQuestionType question types
• Ensure API endpoints handle new question types
• Agree on event type with the frontend developer. Ensure frontend sends correct question types to backend