Add lead workflows, PDF signing, AR projects and photo gallery integration

GasTankAR/Views/Leads/Detail/LeadFileViewModel.swift

@@ -0,0 +1,33 @@
+import Foundation
+import Observation
+
+@MainActor
+@Observable
+final class LeadFileViewModel {
+    private(set) var url: URL?
+    private(set) var message: LocalizedStringResource?
+    private(set) var needsLogin = false
+    private(set) var allowsRetry = true
+    private var generation = 0
+
+    func load(using download: () async throws -> URL) async {
+        generation += 1
+        let request = generation
+        url = nil
+        message = nil
+        needsLogin = false
+        allowsRetry = true
+        do {
+            let result = try await download()
+            try Task.checkCancellation()
+            guard request == generation else { return }
+            url = result
+        } catch is CancellationError {
+        } catch {
+            guard request == generation, !Task.isCancelled else { return }
+            message = error.leadFileMessage
+            needsLogin = error as? LeadError == .unauthorized
+            allowsRetry = (error as? LeadError)?.allowsRetry ?? true
+        }
+    }
+}