[relay] use exposed address for healthcheck TLS validation (#4872)

* fix(relay): use exposed address for healthcheck TLS validation

Healthcheck was using listen address (0.0.0.0) instead of exposed address
(domain name) for certificate validation, causing validation to always fail.

Now correctly uses the exposed address where the TLS certificate is valid,
matching real client connection behavior.

* - store exposedAddress directly in Relay struct instead of parsing on every call
- remove unused parseHostPort() function
- remove unused ListenAddress() method from ServiceChecker interface
- improve error logging with address context

* [relay/healthcheck] Remove QUIC health check logic, update WebSocket validation flow

Refactored health check logic by removing QUIC-specific connection validation and simplifying logic for WebSocket protocol. Adjusted certificate validation flow and improved handling of exposed addresses.

* [relay/healthcheck] Fix certificate validation status during health check

---------

Co-authored-by: Maycon Santos <mlsmaycon@gmail.com>

relay/server/server.go

@@ -28,8 +28,6 @@ type ListenerConfig struct {
 // It is the gate between the WebSocket listener and the Relay server logic.
 // In a new HTTP connection, the server will accept the connection and pass it to the Relay server via the Accept method.
 type Server struct {
-	listenAddr string
-
 	relay       *Relay
 	listeners   []listener.Listener
 	listenerMux sync.Mutex
@@ -62,8 +60,6 @@ func NewServer(config Config) (*Server, error) {
 
 // Listen starts the relay server.
 func (r *Server) Listen(cfg ListenerConfig) error {
-	r.listenAddr = cfg.Address
-
 	wSListener := &ws.Listener{
 		Address:   cfg.Address,
 		TLSConfig: cfg.TLSConfig,
@@ -139,6 +135,6 @@ func (r *Server) ListenerProtocols() []protocol.Protocol {
 	return result
 }
 
-func (r *Server) ListenAddress() string {
-	return r.listenAddr
+func (r *Server) ExposedAddress() string {
+	return r.relay.ExposedAddress()
 }