[UX] Alert system improvements

[erikdarlingdata]

Summary

The alert system works but has UX gaps identified across multiple reviews. Improvements to email content, discoverability, and configuration.

Source: Comprehensive themed agent review (UX Designer + Developer)
Note: Alert persistence bug was #44, already fixed and closed.

Checklist

Email Improvements

• Add server name to email subject (already implemented)
• Email body: include current value, threshold, and affected queries (already implemented)
• Validate SMTP connection before saving settings (PR Alert UX: preview text, SMTP validation, CPU default note (#109) #125: "Validate Settings" button)

Configuration UX

• Add "Restore Defaults" button for thresholds (PR Add Restore Defaults button and alert threshold validation (#109) #123)
• Explain why Lite CPU default (80%) differs from Dashboard (90%) (PR Alert UX: preview text, SMTP validation, CPU default note (#109) #125)
• Add validation: blocking threshold > 0, CPU threshold 1-100 (PR Add Restore Defaults button and alert threshold validation (#109) #123)
• Show preview text: "Will alert when blocking > X seconds" (PR Alert UX: preview text, SMTP validation, CPU default note (#109) #125)

Notification UX

• Add alert badge/count to Alerts button in sidebar
• "Snooze until" option Closed — existing acknowledge/dismiss workflow is sufficient
• Tray balloon duration Won't fix — OS-controlled on Windows 10+

Developer Fixes

• EmailAlertService.Current static Deferred — works fine, purely cosmetic refactor
• _alertLog O(n) Not a real issue — RemoveRange with 1000-cap is negligible

Status

Only remaining item is the sidebar alert badge. All other items resolved or intentionally deferred.