Terraform Module — AWS VPC + ECS Fargate

## Task
Reusable Terraform module for production AWS infrastructure.

## Requirements
- Provider: AWS
- Terraform 1.5+
- Module structure with inputs/outputs

## Architecture
```
                    ┌─────────────────────────────────────┐
                    │              VPC                     │
Internet ─── ALB ──►│  Public Subnet  │  Private Subnet   │
                    │   (NAT GW)     │  (ECS Fargate)    │
                    │                │  (RDS PostgreSQL)  │
                    └─────────────────────────────────────┘
```

## Module Structure
```
modules/
├── vpc/           # VPC, subnets, NAT GW, route tables
├── ecs/           # ECS cluster, task def, service, auto-scaling
├── alb/           # Application Load Balancer, target groups, listeners
├── rds/           # RDS PostgreSQL, subnet group, security group
├── monitoring/    # CloudWatch dashboards, alarms, log groups
└── main.tf        # Compose modules together
```

## Key Variables
```hcl
variable "environment" { description = "dev/staging/prod" }
variable "app_name"     { description = "Application name for resource naming" }
variable "app_image"    { description = "Docker image URI" }
variable "app_port"     { description = "Container port" default = 3000 }
variable "cpu"          { default = 256 }  # Fargate CPU units
variable "memory"       { default = 512 }  # Fargate memory MB
variable "desired_count" { default = 2 }   # ECS task count
variable "db_instance"  { default = "db.t4g.micro" }
```

## Implementation Notes
1. Multi-AZ: spread across 2-3 AZs for availability
2. Security groups: least privilege (app → RDS on 5432 only)
3. Auto-scaling: CPU-based with min 2 / max 10 tasks
4. RDS: encrypted at rest, automated backups, 7-day retention
5. ALB: HTTPS with ACM certificate, HTTP → HTTPS redirect
6. Outputs: ALB URL, RDS endpoint, ECS cluster name, CloudWatch dashboard URL