feat(v2.2.0): add foreground monitoring, notifications, and smarter diffs

- implement “Check All” sweep for tracked domains
- add local notifications for changes and certificate expiration
- introduce change severity filtering (low/medium/high)
- enhance change summaries and diff readability
- add certificate expiration tracking and alerts
- improve watchlist indicators for changes
- add sweep summary screen
- optimize performance for larger watchlists

1 files changed, 89 insertions, 0 deletions

diff --git a/DomainDig/LocalNotificationService.swift b/DomainDig/LocalNotificationService.swift
new file mode 100644
index 0000000..450d844
--- /dev/null
+++ b/DomainDig/LocalNotificationService.swift
@@ -0,0 +1,89 @@
+import Foundation
+import UserNotifications
+
+@MainActor
+final class LocalNotificationService {
+    static let shared = LocalNotificationService()
+
+    private init() {}
+
+    func configureForegroundPresentation() {
+        UNUserNotificationCenter.current().delegate = NotificationCenterDelegate.shared
+    }
+
+    func requestAuthorizationIfNeeded() async -> Bool {
+        let center = UNUserNotificationCenter.current()
+        let settings = await center.notificationSettings()
+
+        switch settings.authorizationStatus {
+        case .authorized, .provisional, .ephemeral:
+            return true
+        case .notDetermined:
+            return (try? await center.requestAuthorization(options: [.alert, .badge, .sound])) ?? false
+        case .denied:
+            return false
+        @unknown default:
+            return false
+        }
+    }
+
+    func notifyDomainEvent(domain: String, message: String, severity: ChangeSeverity) async {
+        await schedule(
+            identifier: "domain-change-\(domain)",
+            title: domain,
+            body: message,
+            interruptionLevel: severity == .high ? .timeSensitive : .active
+        )
+    }
+
+    func notifyCertificateWarning(domain: String, daysRemaining: Int) async {
+        await schedule(
+            identifier: "cert-warning-\(domain)",
+            title: domain,
+            body: "Certificate expires in \(daysRemaining) days",
+            interruptionLevel: .timeSensitive
+        )
+    }
+
+    func notifySweepComplete(summary: BatchSweepSummary) async {
+        let body = "\(summary.changedDomains) changed, \(summary.warningDomains) warnings, \(summary.unchangedDomains) unchanged"
+        await schedule(
+            identifier: "sweep-complete",
+            title: summary.source == .watchlistRefresh ? "Check All Complete" : "Batch Complete",
+            body: body,
+            interruptionLevel: .active
+        )
+    }
+
+    private func schedule(
+        identifier: String,
+        title: String,
+        body: String,
+        interruptionLevel: UNNotificationInterruptionLevel
+    ) async {
+        let content = UNMutableNotificationContent()
+        content.title = title
+        content.body = body
+        content.sound = .default
+        content.interruptionLevel = interruptionLevel
+
+        let request = UNNotificationRequest(
+            identifier: identifier,
+            content: content,
+            trigger: UNTimeIntervalNotificationTrigger(timeInterval: 0.1, repeats: false)
+        )
+
+        try? await UNUserNotificationCenter.current().add(request)
+    }
+}
+
+private final class NotificationCenterDelegate: NSObject, UNUserNotificationCenterDelegate {
+    static let shared = NotificationCenterDelegate()
+
+    func userNotificationCenter(
+        _ center: UNUserNotificationCenter,
+        willPresent notification: UNNotification
+    ) async -> UNNotificationPresentationOptions {
+        [.banner, .list, .sound]
+    }
+}