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/Inbox/InboxViewModel.swift

@@ -91,6 +91,12 @@ final class InboxViewModel: ObservableObject {
             if rows.isEmpty && !failures.isEmpty {
                 errorMessage = "Couldn't load any PRs (\(failures.count) repo(s) failed). Check the Logs screen."
             }
+            // When notifications are on, poll after a foreground load so state
+            // seeds and changes are caught promptly (not just on the ~15-min
+            // background task).
+            if SettingsStore.shared.notificationsEnabled {
+                Task { await NotificationService.shared.poll() }
+            }
         } catch {
             LogStore.shared.log(.error, "Inbox load failed: \(error.localizedDescription)")
             errorMessage = error.localizedDescription