Add encrypted key support for chat and nodes

Introduces encrypted private key storage for nodes and users, updates chat message schema to support sender-side encryption, and adds supporting libraries and tests for cryptographic signing and identity unlock flows. Includes new database migrations, API route updates, and React components for identity unlock prompts.

src/lib/contexts/AuthContext.test.ts

@@ -0,0 +1,52 @@
+/**
+ * AuthContext Type Tests
+ * 
+ * Tests the AuthContext interface updates for cryptographic user signing
+ * Validates: Requirements US-1.1, US-1.2, US-1.4, US-1.5
+ */
+
+import { describe, it, expect } from 'vitest';
+import type { User } from './AuthContext';
+
+describe('AuthContext Interface', () => {
+  it('should include cryptographic fields in User interface', () => {
+    // Create a user object with all required fields
+    const user: User = {
+      id: '1',
+      handle: 'testuser',
+      displayName: 'Test User',
+      avatarUrl: 'https://example.com/avatar.jpg',
+      did: 'did:synapsis:test123',
+      publicKey: 'test-public-key',
+      privateKeyEncrypted: 'encrypted-key',
+    };
+
+    // Verify all fields are present
+    expect(user.id).toBe('1');
+    expect(user.handle).toBe('testuser');
+    expect(user.displayName).toBe('Test User');
+    expect(user.avatarUrl).toBe('https://example.com/avatar.jpg');
+    expect(user.did).toBe('did:synapsis:test123');
+    expect(user.publicKey).toBe('test-public-key');
+    expect(user.privateKeyEncrypted).toBe('encrypted-key');
+  });
+
+  it('should allow optional cryptographic fields', () => {
+    // Create a user object without cryptographic fields
+    const user: User = {
+      id: '1',
+      handle: 'testuser',
+      displayName: 'Test User',
+    };
+
+    // Verify basic fields are present
+    expect(user.id).toBe('1');
+    expect(user.handle).toBe('testuser');
+    expect(user.displayName).toBe('Test User');
+    
+    // Verify cryptographic fields are optional
+    expect(user.did).toBeUndefined();
+    expect(user.publicKey).toBeUndefined();
+    expect(user.privateKeyEncrypted).toBeUndefined();
+  });
+});