IAV-497/refactor: Simplify customer care agent configuration entities

🎯 Objective

Simplify customer care agent configuration entities to improve maintainability and performance.

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📊 Key Changes

1. AgentNotificationConfig

Before: Multiple records per agent (one per event)
After: Single record per agent

• ➕ Added: newTicketCreatedEnabled, ticketPendingEnabled, ticketReopenedEnabled
• ➖ Removed: notificationEvent, emailEnabled, whatsappEnabled, telegramEnabled, enabled
• 🔄 Changed: Unique constraint (agent_id, event) → (agent_id)
• 📝 Channel activation now implicit (determined by presence of contact info)

2. AgentObjective

• ➖ Removed: priorityOrder field

3. AgentWorkingHours

• ➕ Added: startTime, endTime for global working hours

4. WorkingDay (renamed from DailySchedule)

• 🔄 Renamed: DailySchedule → WorkingDay
• ➖ Removed: startTime, endTime (inherited from parent)

Closes IAV-497