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

GasTankAR/Services/Signing/LeadSignedPDFUploadService.swift

@@ -0,0 +1,27 @@
+import Foundation
+
+enum LeadPDFUploadResult: Sendable {
+    case uploaded
+    case simulated
+}
+
+@MainActor
+protocol LeadSignedPDFUploadService {
+    var isSimulation: Bool { get }
+    func upload(_ files: [URL], leadID: String, offerID: String, salesCode: String) async throws -> LeadPDFUploadResult
+}
+
+/// UI demonstration until the PDF upload endpoint is available. Sends no data.
+struct StubLeadSignedPDFUploadService: LeadSignedPDFUploadService {
+    let isSimulation = true
+    var delay: Duration = .seconds(2)
+
+    func upload(_ files: [URL], leadID: String, offerID: String, salesCode: String) async throws -> LeadPDFUploadResult {
+        guard !files.isEmpty, files.allSatisfy({ FileManager.default.fileExists(atPath: $0.path) }) else {
+            throw PDFSigningError.invalidDocument
+        }
+        try await Task.sleep(for: delay)
+        try Task.checkCancellation()
+        return .simulated
+    }
+}