feat: implement Haptika PPG and Watch V1

packages/react-native-haptika-ppg/ios/Safety/PPGThermalMonitor.swift

@@ -0,0 +1,18 @@
+import Foundation
+
+struct PPGThermalMonitor {
+  func currentState() -> ThermalState {
+    switch ProcessInfo.processInfo.thermalState {
+    case .nominal:
+      return .nominal
+    case .fair:
+      return .fair
+    case .serious:
+      return .serious
+    case .critical:
+      return .critical
+    @unknown default:
+      return .unknown
+    }
+  }
+}

packages/react-native-haptika-ppg/ios/Safety/PPGThermalSafetyPolicy.swift

@@ -0,0 +1,17 @@
+import Foundation
+
+/// Pure, testable safety gate used before and during camera acquisition.
+/// Serious and critical states stop the measurement; unknown is conservative
+/// only in the sense that no torch escalation is attempted elsewhere.
+public enum PPGThermalSafetyPolicy {
+  public static func shouldStopMeasurement(forStateName stateName: String) -> Bool {
+    switch stateName.lowercased() {
+    case "serious", "critical":
+      return true
+    case "nominal", "fair", "unknown":
+      return false
+    default:
+      return false
+    }
+  }
+}