fix: corrigir expiração de token e padronizar constantes

- Substitui LocalDateTime.now() por Instant.now() no issuedAt — a string
  produzida por LocalDateTime não contém timezone e era interpretada como
  hora local pelo browser, fazendo o frontend calcular expiresAt errado e
  nunca deslogar o usuário quando o token vencia.
- Cria TokenConstants com ACCESS_TOKEN_EXPIRY_SECONDS e
  REFRESH_TOKEN_EXPIRY_SECONDS, eliminando os valores hardcoded em
  LoginUseCase e RefreshTokenUseCase.
- Remove imports não utilizados em AuthController.

closes #24

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/net/beetechgroup/beetask/interfaceadapters/controllers/auth/AuthController.java

@@ -19,9 +19,6 @@ import net.beetechgroup.beetask.usecase.user.create.CreateUserInput;
 import net.beetechgroup.beetask.usecase.user.create.CreateUserOutput;
 import net.beetechgroup.beetask.usecase.user.create.CreateUserUseCase;
 
-import java.time.LocalDateTime;
-import java.util.List;
-
 import io.quarkus.security.Authenticated;
 import io.quarkus.security.identity.SecurityIdentity;
 import jakarta.ws.rs.GET;

backend/src/main/java/net/beetechgroup/beetask/usecase/auth/TokenConstants.java

@@ -0,0 +1,9 @@
+package net.beetechgroup.beetask.usecase.auth;
+
+public final class TokenConstants {
+
+    public static final long ACCESS_TOKEN_EXPIRY_SECONDS = 3600L;   // 1 hour
+    public static final long REFRESH_TOKEN_EXPIRY_SECONDS = 86400L; // 24 hours
+
+    private TokenConstants() {}
+}

backend/src/main/java/net/beetechgroup/beetask/usecase/auth/login/LoginUseCase.java

@@ -3,9 +3,10 @@ package net.beetechgroup.beetask.usecase.auth.login;
 import io.smallrye.jwt.build.Jwt;
 import net.beetechgroup.beetask.entities.User;
 import net.beetechgroup.beetask.entities.organization.UserOrganization;
+import net.beetechgroup.beetask.usecase.auth.TokenConstants;
 import net.beetechgroup.beetask.usecase.repository.UserRepository;
 
-import java.time.LocalDateTime;
+import java.time.Instant;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Objects;
@@ -51,7 +52,7 @@ public class LoginUseCase {
                 .upn(user.getEmail())
                 .groups(groups)
                 .claim("name", user.getName())
-                .expiresIn(3600)
+                .expiresIn(TokenConstants.ACCESS_TOKEN_EXPIRY_SECONDS)
                 .sign();
 
         List<LoginOutput.OrganizationOutput> orgs = userOrganizations.stream()
@@ -69,7 +70,7 @@ public class LoginUseCase {
 
         String refreshToken = Jwt.issuer(this.issuer)
                 .upn(user.getEmail())
-                .expiresIn(86400) // 24 hours
+                .expiresIn(TokenConstants.REFRESH_TOKEN_EXPIRY_SECONDS)
                 .sign();
 
         LOGGER.infof("Login completed for user %s with %d organizations", user.getEmail(), orgs.size());
@@ -79,8 +80,8 @@ public class LoginUseCase {
                 Objects.nonNull(user.getPhoto()) ? user.getPhoto() : "https://ui-avatars.com/api/?name=" + user.getName().replace(" ", "+") + "&background=random",
                 token,
                 refreshToken,
-                3600L,
+                TokenConstants.ACCESS_TOKEN_EXPIRY_SECONDS,
-                LocalDateTime.now().toString(),
+                Instant.now().toString(),
                 orgs
         );
     }

backend/src/main/java/net/beetechgroup/beetask/usecase/auth/refresh/RefreshTokenUseCase.java

@@ -5,11 +5,12 @@ import io.smallrye.jwt.auth.principal.ParseException;
 import io.smallrye.jwt.build.Jwt;
 import net.beetechgroup.beetask.entities.User;
 import net.beetechgroup.beetask.entities.organization.UserOrganization;
+import net.beetechgroup.beetask.usecase.auth.TokenConstants;
 import net.beetechgroup.beetask.usecase.auth.login.LoginOutput;
 import net.beetechgroup.beetask.usecase.repository.UserRepository;
 import org.eclipse.microprofile.jwt.JsonWebToken;
 
-import java.time.LocalDateTime;
+import java.time.Instant;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Objects;
@@ -58,13 +59,12 @@ public class RefreshTokenUseCase {
                     .upn(user.getEmail())
                     .groups(groups)
                     .claim("name", user.getName())
-                    .expiresIn(3600)
+                    .expiresIn(TokenConstants.ACCESS_TOKEN_EXPIRY_SECONDS)
                     .sign();
 
-            // Generate a new refresh token (also a JWT but with longer expiration)
             String newRefreshToken = Jwt.issuer(this.issuer)
                     .upn(user.getEmail())
-                    .expiresIn(86400) // 24 hours
+                    .expiresIn(TokenConstants.REFRESH_TOKEN_EXPIRY_SECONDS)
                     .sign();
 
             List<LoginOutput.OrganizationOutput> orgs = userOrganizations.stream()
@@ -87,8 +87,8 @@ public class RefreshTokenUseCase {
                     Objects.nonNull(user.getPhoto()) ? user.getPhoto() : "https://ui-avatars.com/api/?name=" + user.getName().replace(" ", "+") + "&background=random",
                     newToken,
                     newRefreshToken,
-                    3600L,
+                    TokenConstants.ACCESS_TOKEN_EXPIRY_SECONDS,
-                    LocalDateTime.now().toString(),
+                    Instant.now().toString(),
                     orgs
             );
         } catch (ParseException e) {