Add validation for SECRET_KEY and FIRST_SUPERUSER_PASSWORD with environment-specific rules

- Enforced minimum length and security standards for `SECRET_KEY` (32 chars, random value required in production).
- Added checks for strong `FIRST_SUPERUSER_PASSWORD` (min 12 chars with mixed case, digits).
- Updated `.env.template` with guidelines for secure configurations.
- Added `test_config.py` to verify validations for environment configurations, passwords, and database URLs.

.env.template

@@ -12,14 +12,19 @@ DATABASE_URL=postgresql://${POSTGRES_USER}:${POSTGRES_PASSWORD}@${POSTGRES_HOST}
 
 # Backend settings
 BACKEND_PORT=8000
-SECRET_KEY=your_secret_key_here
+# CRITICAL: Generate a secure SECRET_KEY for production!
+# Generate with: python -c 'import secrets; print(secrets.token_urlsafe(32))'
+# Must be at least 32 characters
+SECRET_KEY=your_secret_key_here_REPLACE_WITH_GENERATED_KEY_32_CHARS_MIN
 ENVIRONMENT=development
 DEBUG=true
 BACKEND_CORS_ORIGINS=["http://localhost:3000"]
 FIRST_SUPERUSER_EMAIL=admin@example.com
-FIRST_SUPERUSER_PASSWORD=Admin123
+# IMPORTANT: Use a strong password (min 12 chars, mixed case, digits)
+# Default weak passwords like 'Admin123' are rejected
+FIRST_SUPERUSER_PASSWORD=YourStrongPassword123!
 
 # Frontend settings
 FRONTEND_PORT=3000
 NEXT_PUBLIC_API_URL=http://localhost:8000
-NODE_ENV=development
+NODE_ENV=development