Linode Instance Template for Coder

This PR adds a comprehensive Terraform template for provisioning Linode instances as Coder workspaces.

🎯 Features

• 11 Global Regions: US, EU, APAC coverage
• 6 Instance Types: From Nanode 1GB to 32GB
• 9 OS Images: Ubuntu, Debian, CentOS, Fedora, AlmaLinux, Rocky
• Persistent Storage: 10GB-1TB configurable volumes
• Coder Integration: Agent, code-server, JetBrains Gateway
• Cloud-init Setup: Automated configuration

🔧 Technical Improvements

• Fixed storage size handling with proper number validation
• Removed unsupported linode_volume_attachment resource
• Implemented volume lifecycle management
• Added comprehensive documentation

📍 Template Location

registry/toti85/templates/linode-linux/

✅ Testing

• Terraform validation passed
• All required files present
• Cloud-config template validated

/claim #210