feat(blog): reaction milestone emails, unified notification mailer, and mobile UI refinements

[trtajim]

Summary

This PR introduces reaction milestone email notifications, consolidates all blog email notifications into a single reusable class, and refines the mobile UI on blog pages.

Key Changes:

1. Milestone-Based Reaction Notifications:

   • Sends notification emails to blog authors only at key milestones: 1 (first reaction), 10, 25, 50, 100, 250, 500, 1000, and every 500 thereafter.
   • Prevents email spam while keeping authors engaged when their posts reach major audience milestones.

2. Unified Notification Mailer:

   • Replaced separate mail classes with a single reusable BlogNotificationMail with static factories:
     • BlogNotificationMail::forComment($blog, $comment)
     • BlogNotificationMail::forReactionMilestone($blog, $reactor, $count)
   • Reuses the standard emails.bulk_announcement Blade template.

3. Mobile & UX Refinements:

   • Comment Deletion on Touch Screens: Made the delete button always visible on mobile viewports (opacity-100 sm:opacity-0 sm:group-hover:opacity-100) so mobile users can easily delete their comments without hover states.
   • Minimal "Write for Us" Callout: Replaced the bulky full-width CTA with a sleek, compact 1-line callout.

4. Testing & QA:

   • Added Pest feature tests for milestone notifications and self-reaction suppression.
   • 57 passing tests (193 assertions) across PHP 8.3, 8.4, 8.5 with all formatters and linters passing.