feat: add Voxtral WebSocket client with connect/send/receive

MyVoxtral/MyVoxtral/Network/VoxtralWebSocketClient.swift

@@ -0,0 +1,90 @@
+import Foundation
+
+@MainActor
+final class VoxtralWebSocketClient {
+    private var webSocketTask: URLSessionWebSocketTask?
+    private var session: URLSession?
+    private let encoder = JSONEncoder()
+
+    var onEvent: ((VoxtralEvent) -> Void)?
+
+    func connect(apiKey: String, delayMs: Int) {
+        guard let url = URL(string: "wss://api.mistral.ai/v1/audio/transcriptions/realtime") else { return }
+
+        var request = URLRequest(url: url)
+        request.setValue("Bearer \(apiKey)", forHTTPHeaderField: "Authorization")
+
+        session = URLSession(configuration: .default)
+        webSocketTask = session?.webSocketTask(with: request)
+        webSocketTask?.resume()
+
+        // Send session config
+        let config = SessionUpdateMessage(
+            session: SessionConfig(
+                audioFormat: AudioFormatConfig(),
+                targetStreamingDelayMs: delayMs
+            )
+        )
+        sendJSON(config)
+
+        // Start receiving
+        receiveLoop()
+    }
+
+    func sendAudio(_ pcmData: Data) {
+        let base64 = pcmData.base64EncodedString()
+        let msg = AudioAppendMessage(audio: base64)
+        sendJSON(msg)
+    }
+
+    func flush() {
+        sendJSON(AudioFlushMessage())
+    }
+
+    func disconnect() {
+        sendJSON(AudioEndMessage())
+        webSocketTask?.cancel(with: .normalClosure, reason: nil)
+        webSocketTask = nil
+        session?.invalidateAndCancel()
+        session = nil
+    }
+
+    private func sendJSON<T: Encodable>(_ value: T) {
+        guard let data = try? encoder.encode(value),
+              let string = String(data: data, encoding: .utf8) else { return }
+        webSocketTask?.send(.string(string)) { error in
+            if let error {
+                print("WebSocket send error: \(error)")
+            }
+        }
+    }
+
+    private func receiveLoop() {
+        webSocketTask?.receive { [weak self] result in
+            switch result {
+            case .success(let message):
+                switch message {
+                case .string(let text):
+                    if let data = text.data(using: .utf8) {
+                        let event = parseVoxtralEvent(from: data)
+                        Task { @MainActor in
+                            self?.onEvent?(event)
+                        }
+                    }
+                case .data(let data):
+                    let event = parseVoxtralEvent(from: data)
+                    Task { @MainActor in
+                        self?.onEvent?(event)
+                    }
+                @unknown default:
+                    break
+                }
+                self?.receiveLoop()
+            case .failure(let error):
+                Task { @MainActor in
+                    self?.onEvent?(.error("Connection lost: \(error.localizedDescription)"))
+                }
+            }
+        }
+    }
+}