container-creation: cleanup and document

[runleveldev]

Issue: Refactor and document the create-container service for clarity and completeness

Description:
The create-container service is currently under-documented and missing several essential components required for full functionality. The repository structure and documentation make it difficult to understand, extend, or deploy the service reliably.

Recommendation:

• Update the README with complete setup, usage, and dependency instructions
• Restore or recreate missing configuration files (e.g., SSH configs, helper scripts)
• Restructure the repository for logical organization of code, configs, and assets
• Add inline documentation and comments for key scripts and modules
• Simplify and modularize logic to improve maintainability and composability

Benefits:

• Makes the service easier to deploy and contribute to
• Reduces onboarding time for new developers
• Improves maintainability and long-term reliability
• Aligns with best practices for open-source project structure

[runleveldev]

RFC: From #72:

I want to throw out this mass of BASH and replace it with an actual system using pure NodeJS handled by create-a-container. All "frontends" (ssh, GH Actions, etc.) should just call back to the /containers/new API. We especially need to eliminate the mass of nested-ssh calls as root to other servers. We then need to audit authorized_keys because I'm afraid there's been a lot of over-provisioning for permissions. In particular, all calls to pct and family should be replaced by calls to the Proxmox API and use the user's credentials instead of root's.