feat(websocket): add WebSocket Helper with RFC 6455 compliance

Add comprehensive WebSocket support for v-hono framework, inspired by Hono.js WebSocket Helper.

Features:
- upgrade_websocket() function for WebSocket route handlers
- Event-based callbacks: on_open, on_message, on_close, on_error
- WSContext with send(), send_bytes(), send_json(), close() methods
- Connection state tracking (connecting, open, closing, closed)
- Configurable options: ping_interval, max_message_size, timeout, protocols
- Subprotocol negotiation support
- Ping/pong keep-alive handling
- Message size validation with 1009 close code
- Integration with picoev and uSockets backends

Protocol Compliance:
- RFC 6455 compliant handshake with Sec-WebSocket-Accept computation
- Frame encoding/decoding with proper masking
- Close handshake with status codes and reasons
- Text and binary message frame support

Testing:
- 13 property-based test files with 82 tests total
- Validates handshake, frame encoding, masking, JSON round-trip
- Tests context preservation, route patterns, connection state
- All existing tests pass (no regressions)

Files added:
- websocket.v: Core WebSocket implementation
- examples/websocket_demo.v: Chat room example
- examples/websocket_test.html: Browser test client
- tests/test_websocket_*.v: Property-based tests

Files modified:
- app.v: Add ws() method for WebSocket routes
- middleware.v: Export WebSocket types and functions
- picoev_server.v: WebSocket upgrade detection
- usockets_server.v: WebSocket upgrade detection
- README.md: WebSocket documentation

app.v

@@ -175,6 +175,35 @@ pub fn (mut app Hono) options(path string, handler fn (mut Context) http.Respons
 	app.context_trie_router.add_route('OPTIONS', path, h)
 }
 
+// ws() - Register a WebSocket route
+// This method registers a WebSocket upgrade handler at the specified path.
+// The factory function receives the HTTP Context and returns WSEvents configuration.
+//
+// Parameters:
+//   path: The route path (supports path parameters like /ws/:room/:id)
+//   factory: A function that receives the HTTP Context and returns WSEvents
+//   options: Optional WebSocket configuration
+//
+// Example:
+//   app.ws('/chat/:room', fn (c Context) WSEvents {
+//       room := c.params['room'] or { 'default' }
+//       return WSEvents{
+//           on_open: fn (mut ws WSContext) {
+//               ws.send('Welcome to room!') or {}
+//           }
+//           on_message: fn (event WSMessageEvent, mut ws WSContext) {
+//               ws.send('Echo: ${event.data}') or {}
+//           }
+//       }
+//   })
+pub fn (mut app Hono) ws(path string, factory WSHandlerFactory, options ...WebSocketOptions) {
+	// Create the WebSocket upgrade handler
+	ws_handler := upgrade_websocket(factory, ...options)
+	
+	// Register as a GET route (WebSocket upgrades use GET method)
+	app.get(path, ws_handler)
+}
+
 // all() 方法 - 为所有 HTTP 方法注册同一个处理器
 pub fn (mut app Hono) all(path string, handler fn (mut Context) http.Response) {
 	app.get(path, handler)