v1.4: Segurança multi-tenant, file serving via API e UX humanizada

-  Validação cross-tenant no login e rotas protegidas
-  File serving via /api/files/{bucket}/{path} (eliminação DNS)
-  Mensagens de erro humanizadas inline (sem pop-ups)
-  Middleware tenant detection via headers customizados
-  Upload de logos retorna URLs via API
-  README atualizado com changelog v1.4 completo

backend/internal/api/handlers/agency_profile.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 
 	"aggios-app/backend/internal/api/middleware"
+	"aggios-app/backend/internal/config"
 	"aggios-app/backend/internal/repository"
 
 	"github.com/google/uuid"
@@ -13,11 +14,13 @@ import (
 
 type AgencyHandler struct {
 	tenantRepo *repository.TenantRepository
+	config     *config.Config
 }
 
-func NewAgencyHandler(tenantRepo *repository.TenantRepository) *AgencyHandler {
+func NewAgencyHandler(tenantRepo *repository.TenantRepository, cfg *config.Config) *AgencyHandler {
 	return &AgencyHandler{
 		tenantRepo: tenantRepo,
+		config:     cfg,
 	}
 }