feat: funciones infra — Docker, deploy, build y health check

Funciones impuras para gestión de contenedores: docker_build_image,
docker_compose_up/down, docker_volume_create/list/remove,
generate_dockerfile, write_dockerfile, go_build_binary, health_check_http,
deploy_app y stop_app. Todas con tests unitarios donde aplica.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

functions/infra/docker_build_image.go

@@ -0,0 +1,51 @@
+package infra
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// DockerBuildImage construye una imagen Docker desde un directorio con Dockerfile.
+// Retorna el image ID de la imagen construida.
+func DockerBuildImage(contextDir, tag string, buildArgs map[string]string) (string, error) {
+	args := []string{"build", "-t", tag}
+
+	for k, v := range buildArgs {
+		args = append(args, "--build-arg", k+"="+v)
+	}
+
+	args = append(args, contextDir)
+
+	out, err := exec.Command("docker", args...).CombinedOutput()
+	if err != nil {
+		return "", fmt.Errorf("docker build %s: %s", tag, strings.TrimSpace(string(out)))
+	}
+
+	// Extraer el image ID de la ultima linea de output
+	// docker build imprime "Successfully built <id>" o con BuildKit "writing image sha256:<id>"
+	lines := strings.Split(strings.TrimSpace(string(out)), "\n")
+	for i := len(lines) - 1; i >= 0; i-- {
+		line := strings.TrimSpace(lines[i])
+		if strings.Contains(line, "Successfully built ") {
+			parts := strings.Fields(line)
+			return parts[len(parts)-1], nil
+		}
+		if strings.Contains(line, "sha256:") {
+			// BuildKit: extraer sha256:...
+			idx := strings.Index(line, "sha256:")
+			id := line[idx:]
+			if sp := strings.IndexAny(id, " \t,"); sp != -1 {
+				id = id[:sp]
+			}
+			return id, nil
+		}
+	}
+
+	// Si no encontramos el ID en el output, inspeccionar por tag
+	inspectOut, err2 := exec.Command("docker", "inspect", "--format", "{{.Id}}", tag).Output()
+	if err2 != nil {
+		return tag, nil
+	}
+	return strings.TrimSpace(string(inspectOut)), nil
+}