Initial commit: Plataforma de Economía

Features:
- React 18 + TypeScript frontend with Vite
- Go + Gin backend API
- PostgreSQL database
- JWT authentication with refresh tokens
- User management (admin panel)
- Docker containerization
- Progress tracking system
- 4 economic modules structure

Fixed:
- Login with username or email
- User creation without required email
- Database nullable timestamps
- API response field naming

backend/internal/config/config.go

@@ -0,0 +1,47 @@
+package config
+
+import (
+	"os"
+	"strconv"
+)
+
+type Config struct {
+	DBHost     string
+	DBPort     int
+	DBUser     string
+	DBPassword string
+	DBName     string
+
+	JWTSecret          string
+	JWTExpirationHours int
+	RefreshExpDays     int
+}
+
+func Load() *Config {
+	return &Config{
+		DBHost:             getEnv("DB_HOST", "localhost"),
+		DBPort:             getEnvAsInt("DB_PORT", 5432),
+		DBUser:             getEnv("DB_USER", "econ_user"),
+		DBPassword:         getEnv("DB_PASSWORD", "econ_pass"),
+		DBName:             getEnv("DB_NAME", "econ_db"),
+		JWTSecret:          getEnv("JWT_SECRET", "your-secret-key-change-in-production"),
+		JWTExpirationHours: 15 * 60, // 15 minutes in minutes (900 minutes = 15 hours)
+		RefreshExpDays:     7,
+	}
+}
+
+func getEnv(key, defaultValue string) string {
+	if value, exists := os.LookupEnv(key); exists {
+		return value
+	}
+	return defaultValue
+}
+
+func getEnvAsInt(key string, defaultValue int) int {
+	if value, exists := os.LookupEnv(key); exists {
+		if intValue, err := strconv.Atoi(value); err == nil {
+			return intValue
+		}
+	}
+	return defaultValue
+}