feat: improve log viewer with auto-scroll and security enhancements

- Add auto-scroll toggle to log panels
- Enhance SSE connection handling with reconnection logic
- Improve HTML escaping in log lines for security
- Update build script to properly handle frontend artifacts
- Add graceful shutdown to backend server
- Update authentication to support configurable username

backend/dist/placeholder.txt

@@ -0,0 +1 @@
+Placeholder for embed

backend/main.go

@@ -10,8 +10,10 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"os/signal"
 	"regexp"
 	"sync"
+	"syscall"
 
 	"github.com/hpcloud/tail"
 )
@@ -23,12 +25,14 @@ var staticFiles embed.FS
 var (
     port     string
     password string
+    username string
 )
 
 // init() é executado antes de main(). É o lugar ideal para configurar flags.
 func init() {
     flag.StringVar(&port, "port", ":8080", "Porta para o servidor web (ex: :8080, 9090)")
     flag.StringVar(&password, "password", "", "Senha para autenticar o acesso à interface web")
+    flag.StringVar(&username, "username", "admin", "Nome de usuário para autenticar o acesso à interface web")
 }
 
 // LogEntry representa uma linha de log
@@ -88,7 +92,9 @@ func handleSSE(w http.ResponseWriter, r *http.Request) {
     w.Header().Set("Content-Type", "text/event-stream")
     w.Header().Set("Cache-Control", "no-cache")
     w.Header().Set("Connection", "keep-alive")
-    w.Header().Set("Access-Control-Allow-Origin", "*")
+    w.Header().Set("Access-Control-Allow-Origin", "http://localhost:8080")
+    w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
+    w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")
 
     clientChan := broker.Subscribe()
     defer broker.Unsubscribe(clientChan)
@@ -96,7 +102,11 @@ func handleSSE(w http.ResponseWriter, r *http.Request) {
     for {
         select {
         case entry := <-clientChan:
-            data, _ := json.Marshal(entry)
+            data, err := json.Marshal(entry)
+            if err != nil {
+                log.Printf("Erro ao serializar entrada de log: %v", err)
+                continue
+            }
             fmt.Fprintf(w, "data: %s\n\n", data)
             flusher.Flush()
         case <-r.Context().Done():
@@ -155,7 +165,7 @@ func authMiddleware(next http.Handler) http.Handler {
             requestAuth(w)
             return
         }
-        usernameMatch := subtle.ConstantTimeCompare([]byte(user), []byte("admin")) == 1
+        usernameMatch := subtle.ConstantTimeCompare([]byte(user), []byte(username)) == 1
         passwordMatch := subtle.ConstantTimeCompare([]byte(pass), []byte(password)) == 1
         if usernameMatch && passwordMatch {
             next.ServeHTTP(w, r)
@@ -182,6 +192,15 @@ func main() {
         os.Exit(1)
     }
 
+    // Configurar tratamento de sinais para desligamento gracioso
+    sigChan := make(chan os.Signal, 1)
+    signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+    go func() {
+        sig := <-sigChan
+        log.Printf("Recebido sinal %v, encerrando servidor...", sig)
+        os.Exit(0)
+    }()
+
     startTailing(logFiles)
 
     distFS, err := fs.Sub(staticFiles, "dist")