feat: Add API key middleware and update configuration to support API key validation

backend/internal/config/config.go

@@ -15,6 +15,7 @@ import (
 // Config represents the application configuration
 type Config struct {
 	Database models.DatabaseConfig
+	APIKey   string
 }
 
 // LoadConfig loads configuration from environment variables and .env file
@@ -31,6 +32,9 @@ func LoadConfig() (*Config, error) {
 		return nil, fmt.Errorf("failed to load database config: %w", err)
 	}
 
+	// Load API key
+	cfg.APIKey = getEnv("API_KEY", "")
+
 	return cfg, nil
 }