## Why

The existing notification API exposes transport-specific message types to consumers, so a fully configured notification sender cannot be substituted without changing consumer code. Before adding further transports, the framework needs a stable service API in which configuration is bound at composition time and consumers provide only a semantically tagged text message.

## What Changes

- **BREAKING** Relocate the notification API and implementations from `com.r35157.libs.notification` to `com.r35157.service.notification`, without compatibility aliases.
- **BREAKING** Replace `BoundNotifier` and `AddressedNotifier` with transport-independent `BoundNotificationService` and destination-only generic `AddressedNotificationService` contracts.
- **BREAKING** Remove the marker and transport-specific message wrappers in favor of `ΩNotificationMessageΩ` directly.
- Rename the Pushover, Discord, and SMTP implementations to notification-service terminology while preserving their current delivery status.
- Validate every notification message before delivery, and make SMTP binding capture both a validated email address and fixed subject.

## Capabilities

### New Capabilities

- `notification-services`: Defines the transport-independent notification API, binding and validation behavior, and the required behavior of the existing Pushover, Discord, and SMTP implementations.

### Modified Capabilities

None.

## Impact

The change replaces the public notification package and its API types, updates all production imports and inline examples, and removes obsolete message classes. Pushover's synchronous HTTP delivery remains functional; Discord webhook and SMTP delivery remain unimplemented. Alarm-specific Pushover code and Nenjim startup composition are unaffected.