[marcel-breuer]

Summary

• Add configurable uptime targets for monitoring groups, CSV reports for the previous month, and opt-in monthly email delivery to verified owners.
• Add opt-in automatic investigating and resolved updates for public status pages, with email notices to verified subscribers.
• Exclude unknown monitoring time and planned maintenance from SLA calculations; keep generated status updates neutral and avoid exposing private incident notes.

Validation

• Docker Pest: SLA report, automatic incident update, status-page API, monitoring-group API, and mobile idempotency scenarios.
• Docker Composer analyse: passed.
• Docker frontend build and Svelte check: passed.
• PHP Pint Laravel rules: passed for changed PHP files.

Closes #1041
Closes #1044