Operation share environment

[Kubaguette]

Description

This PR introduces the new EnvShare feature alongside critical safety checks for environment creation, laying the foundation for our v1.1.0 release.

Key additions & changes:

• EnvShare (Export): Added UI and native Rust-based local storage for GitHub PATs. Users can now export their .envstation.json configurations directly to a public GitHub Gist via a new "Share" button.
• EnvShare (Import): Added "Recreate Environment" flow. Users can paste a Gist URL to instantly clone an environment. The backend fully deserializes the manifest (including custom packages and configurations) to ensure a true 1:1 recreation, complete with real-time UI progress events.
• Directory Collision Protection: Added host-path inference to prevent creating a new environment in a directory that is already claimed by an existing container. This prevents data corruption, confusing IDE attachments, and mount conflicts.
• Documentation: Updated README.md and added comprehensive Mermaid.js sequence diagrams for the EnvShare data flow in ARCHITECTURE.md.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring / Architecture update

Architecture Checklist:

• My code follows the ARCHITECTURE.md guidelines.
• I have routed system commands through the Host-Executor (build_host_command_async) where necessary.
• I have performed a self-review of my own code.