Replace monolithic notification-system-implementation-plan.md with focused
strategic plan (notification-system-plan.md) and detailed implementation
guide (notification-system-implementation.md). Both documents now perfectly
aligned with TimeSafari codebase patterns including:
- Actual Settings type extension pattern (JSON strings for complex objects)
- Real useNotifications composable stub signatures with eslint-disable
- Verified logger exports and safeStringify usage
- Confirmed PlatformServiceMixin.$saveSettings integration
- Validated migration system registerMigration patterns
Documents are production-ready with accurate code examples verified
against actual TimeSafari infrastructure.