Fix/restore alarms after boot

[Apprentice2907]

Description

This pull request fixes an issue where alarms fail to ring after a device reboot.
Android clears all AlarmManager alarms on reboot, and the app previously did not restore them.

This PR adds a BOOT_COMPLETED broadcast receiver on Android that notifies Flutter to restore all enabled alarms using the existing alarm scheduling logic.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (code improvement/cleanup without logical changes)
• UI/Design change

Proposed Changes

• Added an Android BOOT_COMPLETED BroadcastReceiver to detect device reboots
• Forwarded the reboot event to Flutter via an existing MethodChannel
• Implemented alarm restoration logic in Flutter to re-schedule all enabled alarms
• Ensured no direct database access or schema assumptions on the Android side

Fixes #9

Screenshots

Not applicable (background behavior change; no UI changes).

Checklist

• Tests have been added or updated to cover the changes
• Documentation has been updated to reflect the changes
• Code follows the established coding style guidelines
• All tests are passing