Add Share Extension for importing recipes via URL

Adds a Share Extension so users can share URLs from Safari (or any app)
to open the main app with the ImportURLSheet pre-filled. Uses a custom
URL scheme (nextcloud-cookbook://) as the bridge between the extension
and the main app.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Nextcloud Cookbook iOS Client/Views/Tabs/RecipeTabView.swift

@@ -255,10 +255,15 @@ struct RecipeTabView: View {
                 }
             }
         }
-        .sheet(isPresented: $viewModel.showImportURLSheet) {
-            ImportURLSheet { recipeDetail in
-                viewModel.navigateToImportedRecipe(recipeDetail: recipeDetail)
-            }
+        .sheet(isPresented: $viewModel.showImportURLSheet, onDismiss: {
+            viewModel.pendingImportURL = nil
+        }) {
+            ImportURLSheet(
+                onImport: { recipeDetail in
+                    viewModel.navigateToImportedRecipe(recipeDetail: recipeDetail)
+                },
+                initialURL: viewModel.pendingImportURL ?? ""
+            )
             .environmentObject(appState)
         }
         .sheet(isPresented: $showManualReorderSheet) {
@@ -303,6 +308,7 @@ struct RecipeTabView: View {
 
         @Published var showImportURLSheet: Bool = false
         @Published var importedRecipeDetail: RecipeDetail? = nil
+        @Published var pendingImportURL: String? = nil
 
         func navigateToSettings() {
             sidebarPath.append(SidebarDestination.settings)