Initial commit: Identity management component

- Hierarchical user/device identity system with HD key derivation
- Dependency injection for AsyncStorage and Platform
- Self-contained TypeScript declarations
- Ed25519 keypairs managed by IdentityManager
- Deterministic peer ID generation from BIP39 mnemonic

implementations/AsyncStorageAdapter.ts

@@ -0,0 +1,43 @@
+/**
+ * AsyncStorage adapter for React Native
+ */
+
+import type { IIdentityStorage } from '../interfaces/IIdentity';
+
+// AsyncStorage type definition for dependency injection
+interface IAsyncStorage {
+  setItem(key: string, value: string): Promise<void>;
+  getItem(key: string): Promise<string | null>;
+  removeItem(key: string): Promise<void>;
+  getAllKeys(): Promise<string[]>;
+  multiRemove(keys: string[]): Promise<void>;
+}
+
+export class AsyncStorageAdapter implements IIdentityStorage {
+  private asyncStorage: IAsyncStorage;
+
+  constructor(asyncStorage: IAsyncStorage) {
+    this.asyncStorage = asyncStorage;
+  }
+
+  async setItem(key: string, value: string): Promise<void> {
+    await this.asyncStorage.setItem(key, value);
+  }
+
+  async getItem(key: string): Promise<string | null> {
+    return await this.asyncStorage.getItem(key);
+  }
+
+  async removeItem(key: string): Promise<void> {
+    await this.asyncStorage.removeItem(key);
+  }
+
+  async clear(): Promise<void> {
+    // Only clear identity-related keys
+    const keys = await this.asyncStorage.getAllKeys();
+    const identityKeys = keys.filter((key) => key.startsWith('@IdentityManager'));
+    if (identityKeys.length > 0) {
+      await this.asyncStorage.multiRemove(identityKeys);
+    }
+  }
+}