initial commit: Proximity iOS app proposal, full Swift code scaffold, reference backend, testing docs, generated Xcode project

Proximity/Models/ChatMessage.swift

@@ -0,0 +1,26 @@
+import Foundation
+
+/// A single end-to-end encrypted message within a revealed connection.
+struct ChatMessage: Identifiable, Codable, Hashable {
+    let id: UUID
+    let connectionID: UUID
+    let senderID: String
+    let ciphertext: Data
+    let sentAt: Date
+    var deliveredAt: Date?
+    var readAt: Date?
+
+    init(
+        id: UUID = UUID(),
+        connectionID: UUID,
+        senderID: String,
+        ciphertext: Data,
+        sentAt: Date = Date()
+    ) {
+        self.id = id
+        self.connectionID = connectionID
+        self.senderID = senderID
+        self.ciphertext = ciphertext
+        self.sentAt = sentAt
+    }
+}