bug: passwords regenerate on every AWS init, breaking existing resources

[cherriechang]

Problem

pushkin aws init regenerates random passwords on every run, causing authentication failures when resources already exist.

Current Behavior

1. First run: Creates RabbitMQ with password abc123
2. Second run: Generates NEW password xyz789, updates task definitions
3. RabbitMQ container still expects abc123 but API tries xyz789 → Auth failure
4. Same issue with RDS database passwords during migrations

Cause

Line 1817 in aws/index.js/ecsTaskCreator(): (RabbitMQ)

const rabbitPW = Math.random().toString(); // Always generates new password

Line 1199 in aws/index.js/initDb(): (RDS database)

dbPassword = generateSecurePassword(); // Always generates new password

But there are no check for existing passwords in pushkin.yaml

Wanted Behavior

• Resource exist + password in pushkin.yaml → reuse
• Resource don't exist → generate new password and update pushkin.yaml

Extra enhancements

• Use crypto.randomBytes() for password generation instead of Math.random() for both