Add AI pack generation limits and update related components

Commit notes

- Introduced a new GenerationLimits service to manage user-specific generation limits for AI packs. - Updated AIGenerationHandler to check and record generation limits during pack generation. - Enhanced job processing to track generation start and end for rate limiting. - Added new API endpoint to retrieve current generation limits for users. - Updated frontend components to display generation limits and disable generation when limits are reached. - Refactored related models and handlers to accommodate AI pack properties and ensure proper validation.