fix(labels): correct entity label to use entity data instead of stale waypoint/order fallbacks

[janni1288]

What

Fixes the entity label template ('entity-label.php'), which was copy-pasted from 'waypoint-label.php' and still referenced '$waypoint'/'$order', variables that are never passed to 'Entity::label()'.

Why

Related to #182 - while investigating single-entity label generation, found that the existing 'type=entity' label endpoint renders a broken title ("Waypoint Label" instead of the correct label) and contains dead/unreachable fallback code ('$order->trackingNumber') that would throw if '$trackingNumber' were never empty.

Changes

• Title now correctly reflects the entity instead of a waypoint
• QR code and barcode fallbacks use '$entity->qr_code' / '$entity->barcode' instead of the undefined '$order'
• Tracking number fallback uses '$entity->public_id'

Testing

• Verified locally by rendering 'Entity::label()' via Tinker - title now shows correctly
• Existing test 'LabelIdPdfRenderingTest' still passes

Related to #182