Add Notification and Alerts Functionality

Implement a notification system to keep users informed about important updates and insights within the app.

* **Trigger Types:**

* Resume analysis results or competency gaps identified.
* New company or role suggestions.
* Expiring resumes or outdated data detected.
* System updates or personalized career insights.
* **Delivery Channels:**

* In-app notifications center.
* Optional email alerts or push notifications (if supported).
* **User Controls:**

* Allow users to customize which alerts they receive.
* Include a settings panel for notification preferences.
* **Technical Notes:**

* Consider modular architecture (event-based or queue-driven).
* Use a centralized notification service for consistency.

note: divide into sub-tasks please!