feat(chat): Implement end-to-end encrypted swarm messaging system

- Add Swarm Chat documentation with architecture, API endpoints, and security considerations
- Create database schema for chat conversations, messages, and typing indicators
- Implement chat API endpoints for sending, receiving, and managing messages
- Add client-side encryption utilities using RSA-OAEP with SHA-256
- Create chat page UI for viewing conversations and messages
- Add chat type definitions for TypeScript support
- Update database schema with new chat tables and relationships
- Update sidebar navigation to include chat link
- Enable true end-to-end encrypted messaging across swarm nodes without ActivityPub limitations

src/components/Sidebar.tsx

@@ -100,6 +100,14 @@ export function Sidebar() {
                         )}
                     </Link>
                 )}
+                {user && (
+                    <Link href="/chat" className={`nav-item ${pathname?.startsWith('/chat') ? 'active' : ''}`}>
+                        <svg width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+                            <path d="M21 15a2 2 0 0 1-2 2H7l-4 4V5a2 2 0 0 1 2-2h14a2 2 0 0 1 2 2z"></path>
+                        </svg>
+                        <span>Chat</span>
+                    </Link>
+                )}
                 {user && (
                     <Link href="/settings/bots" className={`nav-item ${pathname?.startsWith('/settings/bots') ? 'active' : ''}`}>
                         <BotIcon />