refactor: consolidate KeychainHelper into KeychainManager (#797)

Merge KeychainHelper functionality into KeychainManager to provide
a single, unified API for all keychain operations.

- Remove KeychainHelper.swift and KeychainHelperProtocol
- Add generic save/load/delete methods to KeychainManagerProtocol
- Update NostrIdentityBridge to use KeychainManagerProtocol
- Update FavoritesPersistenceService to use KeychainManagerProtocol
- Update PreviewKeychainManager with new methods
- Update MockKeychain and add MockKeychainHelper typealias for backwards compatibility

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

bitchat/Services/FavoritesPersistenceService.swift

@@ -26,7 +26,7 @@ final class FavoritesPersistenceService: ObservableObject {
 
     private static let storageKey = "chat.bitchat.favorites"
     private static let keychainService = "chat.bitchat.favorites"
-    private let keychain: KeychainHelperProtocol
+    private let keychain: KeychainManagerProtocol
     
     @Published private(set) var favorites: [Data: FavoriteRelationship] = [:] // Noise pubkey -> relationship
     @Published private(set) var mutualFavorites: Set<Data> = []
@@ -35,8 +35,8 @@ final class FavoritesPersistenceService: ObservableObject {
     private var cancellables = Set<AnyCancellable>()
     
     static let shared = FavoritesPersistenceService()
-    
-    init(keychain: KeychainHelperProtocol = KeychainHelper()) {
+
+    init(keychain: KeychainManagerProtocol = KeychainManager()) {
         self.keychain = keychain
         loadFavorites()
         

bitchat/Services/KeychainManager.swift

@@ -15,11 +15,19 @@ protocol KeychainManagerProtocol {
     func getIdentityKey(forKey key: String) -> Data?
     func deleteIdentityKey(forKey key: String) -> Bool
     func deleteAllKeychainData() -> Bool
-    
+
     func secureClear(_ data: inout Data)
     func secureClear(_ string: inout String)
-    
+
     func verifyIdentityKeyExists() -> Bool
+
+    // MARK: - Generic Data Storage (consolidated from KeychainHelper)
+    /// Save data with a custom service name
+    func save(key: String, data: Data, service: String, accessible: CFString?)
+    /// Load data from a custom service
+    func load(key: String, service: String) -> Data?
+    /// Delete data from a custom service
+    func delete(key: String, service: String)
 }
 
 final class KeychainManager: KeychainManagerProtocol {
@@ -309,9 +317,54 @@ final class KeychainManager: KeychainManagerProtocol {
     }
     
     // MARK: - Debug
-    
+
     func verifyIdentityKeyExists() -> Bool {
         let key = "identity_noiseStaticKey"
         return retrieveData(forKey: key) != nil
     }
+
+    // MARK: - Generic Data Storage (consolidated from KeychainHelper)
+
+    /// Save data with a custom service name
+    func save(key: String, data: Data, service customService: String, accessible: CFString?) {
+        var query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: customService,
+            kSecAttrAccount as String: key,
+            kSecValueData as String: data
+        ]
+        if let accessible = accessible {
+            query[kSecAttrAccessible as String] = accessible
+        }
+
+        SecItemDelete(query as CFDictionary)
+        SecItemAdd(query as CFDictionary, nil)
+    }
+
+    /// Load data from a custom service
+    func load(key: String, service customService: String) -> Data? {
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: customService,
+            kSecAttrAccount as String: key,
+            kSecReturnData as String: true
+        ]
+
+        var result: AnyObject?
+        let status = SecItemCopyMatching(query as CFDictionary, &result)
+
+        guard status == errSecSuccess else { return nil }
+        return result as? Data
+    }
+
+    /// Delete data from a custom service
+    func delete(key: String, service customService: String) {
+        let query: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: customService,
+            kSecAttrAccount as String: key
+        ]
+
+        SecItemDelete(query as CFDictionary)
+    }
 }