Restructure step 2: Status as one computed level, the Notifier's real policy, system notifications

- Status: computed from connection, presence, hold, relay, player facts;
  no setters (health writes and HealthStatus gone); pill, strip and
  source line read it; transitions go to the Notifier.
- Notifier: noticeFor(event, context) with self presence, alone, window
  activity, playing and prefs; toasts for joins/leaves/returns/swaps/
  Up next adds (with picture)/problems/chat, the rest logged; while
  sitting out only chat, nudges, starting, Up next (+ joins if chosen);
  alone no social notices; replayed lines logged; owns its toast timer.
- System notifications (flutter_local_notifications: D-Bus on Linux,
  WinRT on Windows) when the window isn't focused; a click focuses it.
- Toasts sit above the control bar and move with it.
- Versions: each member's in the members card and avatar tooltip,
  the server's in the card header; the strip no longer shows it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/pubspec.lock

@@ -230,6 +230,46 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "6.0.0"
+  flutter_local_notifications:
+    dependency: "direct main"
+    description:
+      name: flutter_local_notifications
+      sha256: "9ee28742343dd13df758bb4185e8ded37ac2d1aeca6648c3ba7862c99797517e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "22.3.2"
+  flutter_local_notifications_linux:
+    dependency: transitive
+    description:
+      name: flutter_local_notifications_linux
+      sha256: "3b89a4bf095fa5f8a99beeabf982c5bd506c3ad25e7b9e61da945e994dc5b615"
+      url: "https://pub.dev"
+    source: hosted
+    version: "8.0.2"
+  flutter_local_notifications_platform_interface:
+    dependency: transitive
+    description:
+      name: flutter_local_notifications_platform_interface
+      sha256: "43c3761d916c9bd3d5c7ebbc44d82f4990329840c0c5d62ad5260cc1b5d399bd"
+      url: "https://pub.dev"
+    source: hosted
+    version: "12.2.0"
+  flutter_local_notifications_web:
+    dependency: transitive
+    description:
+      name: flutter_local_notifications_web
+      sha256: "516afaf97a2d1e67a036c6617321b00d205d72f7a67b6eccf936cd565f985878"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.0"
+  flutter_local_notifications_windows:
+    dependency: transitive
+    description:
+      name: flutter_local_notifications_windows
+      sha256: "6f43bdd03b171b7a90f22647506fea33e2bb12294b7c7c7a3d690e960a382945"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.1"
   flutter_localizations:
     dependency: transitive
     description: flutter
@@ -858,6 +898,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.7.12"
+  timezone:
+    dependency: transitive
+    description:
+      name: timezone
+      sha256: "9f4e5a1a0e4fef7dd3424842c0575db01bfb7a11730e8d55753fcd5c5c98767b"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.11.2"
   typed_data:
     dependency: transitive
     description: