feat(apple): transfer controls, progress fixes, and project config

- Sender progress: aggregate only in-flight receivers so the bar clears on
  completion and is order-independent ("Sending to N")
- Add Stop sharing and per-receiver Refuse (pending requests) on the sender
- Fix macOS: raise approval modal above the Share sheet; drive foreground
  state off NSApplication so background notifications fire
- Persist app identity (display name, category) and signing team via
  Info.plist / project.yml / gitignored Local.xcconfig

apple/Signing.xcconfig

@@ -0,0 +1,9 @@
+// Committed signing config. Contains no secrets.
+//
+// Per-developer signing (e.g. DEVELOPMENT_TEAM) goes in Local.xcconfig, which is
+// gitignored. The optional include below means the build still works for anyone
+// who doesn't have a Local.xcconfig — Xcode automatic signing fills in their team.
+//
+// To persist your team across `xcodegen generate`, create apple/Local.xcconfig:
+//   DEVELOPMENT_TEAM = XXXXXXXXXX
+#include? "Local.xcconfig"