Preview diagram and PDF before sharing (iOS + Android)

iOS: route exports through QLPreviewController so users can inspect
before sharing. Android: add a zoomable full-screen diagram preview
with a share button; PDF still goes straight to the share sheet.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cable/Loads/LoadsView.swift

@@ -29,7 +29,8 @@ struct LoadsView: View {
     @State private var overviewExportRequested = false
     @State private var diagramExportRequested = false
     @State private var isExportingOverview = false
-    @State private var overviewShareItem: OverviewShareItem?
+    @State private var previewURL: URL?
+    @State private var previewTempURL: URL?
     @State private var overviewExportError: OverviewExportError?
 
     let system: ElectricalSystem
@@ -219,11 +220,12 @@ struct LoadsView: View {
                 }
             )
         }
-        .sheet(item: $overviewShareItem, onDismiss: {
-            cleanupOverviewShareItem()
-            ReviewPrompt.registerSuccessfulExport()
-        }) { item in
-            ShareSheet(items: item.shareItems)
+        .quickLookPreview($previewURL)
+        .onChange(of: previewURL) { _, newValue in
+            if newValue == nil {
+                cleanupPreview()
+                ReviewPrompt.registerSuccessfulExport()
+            }
         }
         .alert(
             String(localized: "overview.share.error.title", defaultValue: "Export Failed"),
@@ -1106,12 +1108,6 @@ struct LoadsView: View {
 
     // MARK: - PDF Export
 
-    private struct OverviewShareItem: Identifiable {
-        let id = UUID()
-        let shareItems: [Any]
-        let tempURL: URL?
-    }
-
     private struct OverviewExportError: Identifiable {
         let message: String
         var id: String { message }
@@ -1134,7 +1130,8 @@ struct LoadsView: View {
                     "system": snapshot.systemName,
                 ])
                 await MainActor.run {
-                    overviewShareItem = OverviewShareItem(shareItems: [url], tempURL: url)
+                    previewURL = url
+                    previewTempURL = url
                     isExportingOverview = false
                 }
             } catch {
@@ -1164,7 +1161,8 @@ struct LoadsView: View {
                     AnalyticsTracker.log("Diagram Image Shared", properties: [
                         "system": snapshot.systemName,
                     ])
-                    overviewShareItem = OverviewShareItem(shareItems: [url], tempURL: url)
+                    previewURL = url
+                    previewTempURL = url
                 } else {
                     overviewExportError = OverviewExportError(
                         message: String(localized: "overview.share.diagram.error", defaultValue: "Could not generate diagram. Check your internet connection.")
@@ -1284,11 +1282,10 @@ struct LoadsView: View {
         )
     }
 
-    private func cleanupOverviewShareItem() {
-        guard let item = overviewShareItem else { return }
-        overviewShareItem = nil
-        if let url = item.tempURL {
+    private func cleanupPreview() {
+        if let url = previewTempURL {
             try? FileManager.default.removeItem(at: url)
+            previewTempURL = nil
         }
     }
 }