feat: Initial MVP with home server identity model

- User model with Ed25519 keypair identity
- Register/login on home server (creates keypair)
- Join guest servers with signature verification
- Public endpoints for cross-server identity
- Channel and message CRUD
- JWT authentication middleware

Architecture: Home server model, no federation, client-driven sync

lib/server.dart

@@ -0,0 +1,86 @@
+import 'package:chat_server/models.dart';
+import 'package:chat_server/objectbox.g.dart';
+import 'package:hotreloader/hotreloader.dart';
+import 'package:relic/relic.dart';
+
+import 'config/config.dart';
+import 'src/auth/auth_middleware.dart';
+import 'src/handlers/auth_handlers.dart';
+import 'src/handlers/channel_handlers.dart';
+import 'src/handlers/message_handlers.dart';
+import 'src/handlers/public_handlers.dart';
+import 'src/utils/extensions.dart';
+
+// Global ObjectBox store and boxes
+late final Store store;
+late final Box<User> userBox;
+late final Box<Channel> channelBox;
+late final Box<Message> messageBox;
+
+RelicApp? _currentApp;
+
+Future<void> startServer() async {
+  await _currentApp?.close();
+
+  _currentApp = RelicApp()
+    // ============ PUBLIC ENDPOINTS (no auth) ============
+    
+    // Auth
+    ..post('/auth/register', registerHandler)
+    ..post('/auth/login', loginHandler)
+    ..post('/auth/join', joinServerHandler)
+    
+    // Public identity verification (for cross-server)
+    ..get('/.well-known/users/<username>', publicUserHandler)
+    ..get('/.well-known/verify/<userId>', publicVerifyHandler)
+    ..get('/.well-known/server', publicServerInfoHandler)
+    
+    // ============ PROTECTED ENDPOINTS (requires auth) ============
+    ..use('/api', jwtMiddleware)
+    
+    // Current user
+    ..get('/api/me', getMeHandler)
+    
+    // Channels
+    ..get('/api/channels', getChannelsHandler)
+    ..post('/api/channels', createChannelHandler)
+    ..get('/api/channels/<channelId>', getChannelHandler)
+    
+    // Messages
+    ..get('/api/messages', getMessagesHandler)
+    ..post('/api/messages', sendMessageHandler)
+    ..put('/api/messages/<messageId>', editMessageHandler)
+    ..delete('/api/messages/<messageId>', deleteMessageHandler)
+    
+    // ============ LOGGING & FALLBACK ============
+    ..use('/', logRequests())
+    ..fallback = respondWith((_) => Response.notFound());
+
+  print('');
+  print('╔════════════════════════════════════════════╗');
+  print('║  🚀 Server starting...                      ║');
+  print('║  Host: ${Config.serverHost.padRight(34)}║');
+  print('║  URL:  http://localhost:${Config.port.toString().padRight(26)}║');
+  print('╚════════════════════════════════════════════╝');
+  print('');
+
+  await _currentApp!.serve(port: Config.port);
+}
+
+void main() async {
+  // Initialize ObjectBox
+  store = openStore();
+  userBox = store.box<User>();
+  channelBox = store.box<Channel>();
+  messageBox = store.box<Message>();
+
+  // Enable hot reload in development
+  await HotReloader.create(
+    onAfterReload: (ctx) async {
+      print('🔄 Changes detected! Restarting server...');
+      await startServer();
+    },
+  );
+
+  await startServer();
+}