Notifications: iOS notificationSend is a stub

[proggeramlug]

perry_system_notification_send in crates/perry-ui-ios/src/lib.rs:1545 is an empty {}. The macOS twin in crates/perry-ui-macos/src/notifications.rs already wires UNUserNotificationCenter (with an NSUserNotification fallback for unbundled apps).

Scope

• Port the macOS UNMutableNotificationContent + UNTimeIntervalNotificationTrigger + UNNotificationRequest + UNUserNotificationCenter.currentNotificationCenter path into the iOS crate.
• requestAuthorizationWithOptions: needs to fire once at app launch (not per-send) — wire into perry-ui-ios/src/app.rs bootstrap.
• Parity with the TS surface: notificationSend(title, body) in types/perry/system/index.d.ts:53.

Out of scope

Remote/push (separate ticket), scheduling, tap callbacks, background.

[proggeramlug]

Closed — notificationSend ships on both Apple platforms and Android.

• iOS (v0.5.191, commit 6129690): replaced the empty stub with the UNUserNotificationCenter path mirroring the macOS implementation. requestAuthorizationWithOptions: split out into request_authorization() and fired once from PerryAppDelegate.application:didFinishLaunchingWithOptions: instead of per-send. -framework UserNotifications added to the iOS link line.
• Android (v0.5.256, commit 828f04a): pre-fix the JNI call to PerryBridge.sendNotification would have thrown NoSuchMethodError — that Kotlin method didn't exist. Added sendNotification(activity, title, body) with lazy NotificationChannel (API 26+), POST_NOTIFICATIONS gate (API 33+), NotificationCompat.Builder + NotificationManagerCompat.notify with fixed id "perry_notification".hashCode() so subsequent calls replace (mirroring iOS / macOS slot reuse).