Remove built-in TLS support in favor of Nginx termination

This commit eliminates the native TLS implementation from rttys.
Going forward, TLS termination will be handled exclusively by
Nginx reverse proxy. Key changes include:

1. Removed all TLS-related configuration options
2. Deleted certificate handling and encryption logic
3. Simplified network stack to plain TCP only
4. Updated documentation to reflect new architecture

Rationale:
- Delegates TLS to specialized reverse proxy (Nginx)
- Improves security through separation of concerns
- Reduces attack surface of rttys core service
- Enables centralized certificate management
- Facilitates future scalability with proxy layer

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

http.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"bufio"
-	"crypto/tls"
 	"encoding/binary"
 	"errors"
 	"fmt"
@@ -244,24 +243,9 @@ func listenHttpProxy(brk *broker) {
 		log.Fatal().Msg(err.Error())
 	}
 
-	if cfg.WebUISslCert != "" && cfg.WebUISslKey != "" {
-		crt, err := tls.LoadX509KeyPair(cfg.WebUISslCert, cfg.WebUISslKey)
-		if err != nil {
-			log.Fatal().Msg(err.Error())
-		}
-
-		tlsConfig := &tls.Config{Certificates: []tls.Certificate{crt}}
-
-		ln = tls.NewListener(ln, tlsConfig)
-	}
-
 	cfg.HttpProxyPort = ln.Addr().(*net.TCPAddr).Port
 
-	if cfg.WebUISslCert != "" && cfg.WebUISslKey != "" {
-		log.Info().Msgf("Listen http proxy on: %s SSL on", ln.Addr().(*net.TCPAddr))
-	} else {
-		log.Info().Msgf("Listen http proxy on: %s SSL off", ln.Addr().(*net.TCPAddr))
-	}
+	log.Info().Msgf("Listen http proxy on: %s", ln.Addr().(*net.TCPAddr))
 
 	go func() {
 		defer ln.Close()
@@ -344,11 +328,7 @@ func httpProxyRedirect(br *broker, c *gin.Context) {
 			host = c.Request.Host
 		}
 
-		if cfg.WebUISslCert != "" && cfg.WebUISslKey != "" {
-			location = "https://" + host
-		} else {
-			location = "http://" + host
-		}
+		location = "http://" + host
 
 		if cfg.HttpProxyPort != 80 {
 			location += fmt.Sprintf(":%d", cfg.HttpProxyPort)