Fix #944 — one-click snooze from alert tray popup

[erikdarlingdata]

Summary

• Replaces the non-interactive Windows toast for seven fired alerts (CPU, Blocking, Deadlocks, Poison Wait, Long-Running Query, TempDB Space, Long-Running Job) with a custom WPF balloon that has Snooze 15m / 1h / 4h + Dismiss buttons.
• Snooze creates a temporary MuteRule scoped to ServerName + MetricName with the chosen expiration. The existing alert-fire path already honors mute rules for both email and Teams/Slack webhook delivery, so a snooze silences all three channels until it expires.
• Status notifications (Online/Offline + 7 Cleared/Resolved) keep the standard non-interactive balloon — there's nothing to snooze on a "cleared" event.

Addresses the firefighting workflow described in #943, where deadlock alerts kept paging Teams for an hour after the underlying issue was resolved because the rolling-window count still had data points.

Files

• Lite/Controls/SnoozeBalloon.xaml + .xaml.cs (new) — WPF UserControl. Severity icon + color match the alert level. Closes via TaskbarIcon.BalloonClosingEvent after click.
• Lite/Services/SystemTrayService.cs — adds ShowSnoozableNotification(...) using _trayIcon.ShowCustomBalloon(...) with a 15s auto-close.
• Lite/MainWindow.xaml.cs — swaps 7 fired-alert call sites to the new method. The 9 status notifications keep using the standard balloon.

Scope decision

Snooze creates a rule keyed only on ServerName + MetricName. Mid-incident the user wants "shut up about deadlocks on this box for an hour," not "shut up about this exact query." For narrower scoping, Settings → Manage Mute Rules still works.

Test plan

• Trigger an alert (e.g. drop CPU threshold low enough to fire on a busy server).
• Verify the popup shows Title / Message / Snooze 15m, 1h, 4h / Dismiss.
• Click Snooze 1h → confirm a rule appears in Settings → Manage Mute Rules with the right server, metric, and ~1h expiration.
• Confirm follow-up alert checks for that server+metric do not produce a tray popup, email, or Teams/Slack message until the rule expires.
• Click Dismiss on a different alert → confirm no rule is created, popup closes.
• Verify Cleared / Resolved notifications still appear as standard Windows toasts when the underlying condition recovers.

Follow-up (separate PR, not in this branch)

Email body and Teams/Slack webhook payload should also include a one-liner pointing at Settings → Manage Mute Rules for discoverability when the alert lands somewhere other than the desktop. Tracked under #944.

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