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

GasTankAR/Model/LeadARProjectLink.swift

@@ -0,0 +1,16 @@
+import Foundation
+import SwiftData
+
+/// Integration-owned association; AR views never receive this model.
+@Model
+final class LeadARProjectLink {
+    var leadID: String
+    var offerID: String?
+    @Relationship(deleteRule: .nullify) var project: Project?
+
+    init(leadID: String, offerID: String? = nil, project: Project) {
+        self.leadID = leadID
+        self.offerID = offerID
+        self.project = project
+    }
+}