refactor: migrate iOS gateway to unified ws

apps/ios/Sources/Gateway/KeychainStore.swift

@@ -0,0 +1,48 @@
+import Foundation
+import Security
+
+enum KeychainStore {
+    static func loadString(service: String, account: String) -> String? {
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: service,
+            kSecAttrAccount as String: account,
+            kSecReturnData as String: true,
+            kSecMatchLimit as String: kSecMatchLimitOne,
+        ]
+
+        var item: CFTypeRef?
+        let status = SecItemCopyMatching(query as CFDictionary, &item)
+        guard status == errSecSuccess, let data = item as? Data else { return nil }
+        return String(data: data, encoding: .utf8)
+    }
+
+    static func saveString(_ value: String, service: String, account: String) -> Bool {
+        let data = Data(value.utf8)
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: service,
+            kSecAttrAccount as String: account,
+        ]
+
+        let update: [String: Any] = [kSecValueData as String: data]
+        let status = SecItemUpdate(query as CFDictionary, update as CFDictionary)
+        if status == errSecSuccess { return true }
+        if status != errSecItemNotFound { return false }
+
+        var insert = query
+        insert[kSecValueData as String] = data
+        insert[kSecAttrAccessible as String] = kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly
+        return SecItemAdd(insert as CFDictionary, nil) == errSecSuccess
+    }
+
+    static func delete(service: String, account: String) -> Bool {
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: service,
+            kSecAttrAccount as String: account,
+        ]
+        let status = SecItemDelete(query as CFDictionary)
+        return status == errSecSuccess || status == errSecItemNotFound
+    }
+}