fix(apple): show receiver-approval modal on macOS release builds

The approval modal never appeared for a macOS sender: the receiver request
reached the core and even fired its notification, but the modal stayed hidden.

Root cause was observation, not presentation. `RootView` derived `approvals`
and `messages` as `@ObservedObject` in `init` from a freshly built `AppGraph`.
`init` runs on every view re-creation and each run makes a throwaway graph, so
those observed objects were repointed to a dead `ApprovalCoordinator` that never
receives core events — while the persisted `@StateObject graph` (and the models
wired to it) kept the live one. Debug happened not to re-init the view, so it
stayed on the live instance; release re-inits it, exposing the bug.

Move the snackbar + approval modal into an `OverlayLayer` child view that takes
the coordinator/messages as `@ObservedObject` and is constructed in `body` from
the persisted `graph`, so the subscription is always against the live instances.

While here:
- Present the approval only after any open share/QR sheet has actually finished
  dismissing (macOS can't stack sheets), driven off the sheet's real
  `onDismiss` completion via a new `AdaptiveDrawer.onDismissed` hook and
  `SendModel.shareSheetsDismissed` — no wall-clock delay.
- Move the list-level share-sheet state (`shareTargetId`) into `SendModel` so the
  approval flow can dismiss every share surface centrally.
- Add a fallback: pending receiver rows in the Receivers panel now offer an
  Approve action (`SendModel.acceptReceiver`) alongside Refuse, for the case the
  modal didn't surface.

apple/VniDrop/Features/Send/SendScreen.swift

@@ -7,14 +7,18 @@ struct SendScreen: View {
 	@ObservedObject var model: SendModel
 	let windowClass: WindowClass
 
-	/// Transfer whose share panel is presented inline from the list context menu.
-	@State private var shareTarget: Transfer?
 	/// Transfer pending an inline (list-level) delete confirmation.
 	@State private var deleteTarget: Transfer?
 
 	private var outgoing: [Transfer] {
 		model.coreState.transfers.filter { $0.direction == .send }
 	}
+	/// The transfer whose list-level share sheet is open, resolved from the model's
+	/// `shareTargetId` (kept in the model so the approval flow can dismiss it).
+	private var shareTarget: Transfer? {
+		guard let id = model.state.shareTargetId else { return nil }
+		return outgoing.first { $0.transferId == id }
+	}
 	private var selectedTransfer: Transfer? {
 		guard let id = model.state.selectedTransferId else { return nil }
 		return outgoing.first { $0.transferId == id }
@@ -50,9 +54,10 @@ struct SendScreen: View {
 			// composer drawer on the outer body, so the two don't clash). Opens the
 			// share panel over the list without navigating into the transfer detail.
 			.adaptiveDrawer(
-				isPresented: Binding(get: { shareTarget != nil }, set: { if !$0 { shareTarget = nil } }),
+				isPresented: Binding(get: { shareTarget != nil }, set: { if !$0 { model.closeShareTarget() } }),
 				windowClass: windowClass,
-				onDismiss: { shareTarget = nil }
+				onDismiss: model.closeShareTarget,
+				onDismissed: model.shareSheetDidDismiss
 			) {
 				if let shareTarget {
 					TransferSharePanel(model: model, transfer: shareTarget)
@@ -92,7 +97,8 @@ struct SendScreen: View {
 			.adaptiveDrawer(
 				isPresented: Binding(get: { model.state.detailPanel != nil }, set: { _ in }),
 				windowClass: windowClass,
-				onDismiss: model.closeDetailPanel
+				onDismiss: model.closeDetailPanel,
+				onDismissed: model.shareSheetDidDismiss
 			) {
 				if let panel = model.state.detailPanel {
 					DetailPanelContent(model: model, transfer: transfer, panel: panel)
@@ -127,7 +133,7 @@ struct SendScreen: View {
 					.contextMenu {
 						if transfer.ticket != nil {
 							Button {
-								shareTarget = transfer
+								model.openShareTarget(transfer.transferId)
 							} label: {
 								Label(String(localized: L10n.Transfer.shareTitle), systemSymbol: .squareAndArrowUp)
 							}