Implement user notification saving preferences and update DB

[afrinxnahar]

🎯 Problem Statement
Users currently cannot manage which notifications they receive; notification delivery preferences are not saved to the database.

💡 Proposed Solution

• On the user settings page, Notification Preferences , add additional notification with toggles for types: product_updates, usage_alerts etc.
• Create a new table on DB called notification_preferences with the necessary columns
• Add API endpoints to read/update preferences.

📊 Impact Assessment
User Impact: High (gives control over communications).
Development Effort: Low–Medium.
Priority: High.

🧪 Acceptance Criteria

• Settings UI available.
• Preferences saved in DB.
• Notifications respect preferences.
• Migration script for existing users present.

🔗 Related Features
Email templates, mailing flows, admin broadcast tools.

📚 Additional Context
Consider GDPR/consent rules for marketing emails.

📋 Checklist

• DB migration for preferences
• Backend APIs to read/update preferences
• Frontend settings UI
• Notification sending respects preferences
• Tests for preference flows