Add MyDataWatchHandler, handle

SecureStorageSample Watch App/README.md

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+# SecureStorageSample Watch App
+
+A watchOS companion app demonstrating data synchronization with the iOS app using WatchConnectivity.
+
+## Overview
+
+This watch app receives `UserProfile` data synced from the paired iPhone via `WCSession.updateApplicationContext`. It does **not** use LocalData directly for storage—instead, it displays synced data in memory.
+
+## Architecture
+
+```
+SecureStorageSample Watch App/
+├── ContentView.swift           # Displays synced profile data
+├── SecureStorageSampleApp.swift
+├── Protocols/
+│   └── WatchDataHandling.swift # Protocol for payload handlers
+├── State/
+│   └── WatchProfileStore.swift # Holds synced profile in memory
+└── Services/
+    ├── WatchConnectivityService.swift
+    └── Handlers/
+        └── UserProfileWatchHandler.swift
+```
+
+## Data Flow
+
+1. **iOS app** calls `SyncHelper` when storing data with `syncPolicy: .automaticSmall` or `.manual`
+2. `SyncHelper` sends data via `WCSession.updateApplicationContext`
+3. **Watch app** receives context in `WatchConnectivityService`
+4. The service dispatches each payload key to its registered `WatchDataHandling` handler
+5. `UserProfileWatchHandler` decodes the profile and updates `WatchProfileStore`
+
+## Adding New Sync Payloads
+
+1. Create a new handler conforming to `WatchDataHandling`:
+
+```swift
+struct MyDataWatchHandler: WatchDataHandling {
+    let key = "myData"
+    
+    func handle(data: Data) {
+        // Decode and update state
+    }
+}
+```
+
+2. Register it in `WatchConnectivityService.registerDefaultHandlers()`
+
+## Limitations
+
+- **No persistent storage on watch**: Data is held in memory only
+- **One-way sync**: Watch receives data from iPhone; it does not send data back
+- **Simulator limitations**: WatchConnectivity may not work reliably in the simulator
+
+## Requirements
+
+- watchOS 10.0+
+- Paired with iOS app via WatchConnectivity