Add account management options and overlay permission for forward alarms.

Add coin reset and full account data deletion in Options with irreversible
confirmation dialogs. Implement AccountDeletionService to wipe Firestore
user data (todos, coupons, settings) and clear local alarms/widget state.
Request SYSTEM_ALERT_WINDOW so Forward Screen can auto-launch from the home
screen when the display is on.

Co-authored-by: Cursor <cursoragent@cursor.com>