Add push-equivalent notifications via background polling; bump to 3.6

Sideloaded apps can't use APNs (no push entitlement without Apple signing),
so deliver notifications via an iOS BGAppRefreshTask that polls the monitored
repos every ~15 min and fires local notifications (no Apple push needed):
- new PRs that appear in the open set
- CI status changes on existing PRs

Persistence: NotificationState tracks announced PR ids + last-known CI status
so we only fire on actual changes, not every poll. AppDelegate registers the
background task and reschedules the next one. Info.plist gets UIBackgroundModes
fetch + the BGTask identifier. Settings gains a Notifications toggle; also
poll after a foreground inbox load so state seeds and changes are caught
promptly. Bump to 3.6.

GiteaPR/Settings/SettingsView.swift

@@ -7,6 +7,7 @@ struct SettingsView: View {
     @State private var mergeGateMode: MergeGateMode
     @State private var deleteBranchAfterMerge: Bool
     @State private var monitoredRepos: [String]
+    @State private var notificationsEnabled: Bool
     @State private var testResult: TestResult?
     @State private var testing = false
     @State private var showLogoutConfirm = false
@@ -22,6 +23,7 @@ struct SettingsView: View {
         _mergeGateMode = State(initialValue: SettingsStore.shared.mergeGateMode)
         _deleteBranchAfterMerge = State(initialValue: SettingsStore.shared.deleteBranchAfterMerge)
         _monitoredRepos = State(initialValue: SettingsStore.shared.monitoredRepos)
+        _notificationsEnabled = State(initialValue: SettingsStore.shared.notificationsEnabled)
     }
 
     var body: some View {
@@ -66,6 +68,14 @@ struct SettingsView: View {
                     Text("Limit the landing page to specific repos to speed it up. Leave empty to monitor all accessible repos.")
                 }
 
+                Section {
+                    Toggle("Notifications", isOn: $notificationsEnabled)
+                } header: {
+                    Text("Notifications")
+                } footer: {
+                    Text("Check periodically for new PRs and CI status changes, then send a local notification. Best-effort: iOS schedules this opportunistically (~15 min) and only when the app was used recently.")
+                }
+
                 Section("Diagnostics") {
                     NavigationLink("View logs") {
                         LogsView()
@@ -147,6 +157,7 @@ struct SettingsView: View {
         SettingsStore.shared.mergeGateMode = mergeGateMode
         SettingsStore.shared.deleteBranchAfterMerge = deleteBranchAfterMerge
         SettingsStore.shared.monitoredRepos = monitoredRepos
+        SettingsStore.shared.notificationsEnabled = notificationsEnabled
         dismiss()
     }
 }