Guardian notification UI

[Muskanpreet20]

This PR introduces the Guardian Notification system into the Smishing Detection App, enabling real-time alerts, user-defined guardian linking, and notification history — all designed with scalability, modularity, and user experience in mind.

Key Highlights:

• Add Guardian UI: Seamlessly allows users to connect with a guardian using a clean, intuitive interface.
• Notification History Screen: Displays a scrollable list of received alerts, styled for clarity and ease of use.
• Firebase Cloud Messaging (FCM): Fully integrated for real-time push notifications, including channel creation, permission handling, and token retrieval.
• FCM Token Syncing: On login, the app auto-fetches and sends the device token to the backend for seamless messaging capability.
• Retrofit API Setup: Clean implementation to handle login, notification sending, and backend communication.
• MainActivity Enhancements: Modernized with better navigation logic, updated button handling, and improved lifecycle management.
• SettingsActivity Polish: Integrated scroll restoration, theme toggles, and new navigation buttons including Guardian access.

Tested Functionality:

• FCM push notifications successfully displayed on Android 13+.
• Add Guardian UI functional and navigates correctly.
• Token logs appear as expected, ensuring backend sync.
• App launches cleanly and handles screen navigation with no crashes.