Hardened Windows Agent Task Termination and Automatic Cleanup

fix: restore swarm control and windows node connectivity ...

- Resolved LLM provider identification issue in PreferenceService by implementing strict prefix matching and model version parsing.
- Enforced strict tenant-level LLM resolution by removing all system-wide hardcoded fallbacks to 'gemini'.
- Fixed Windows node persistence by updating SchtasksManager to explicitly set the working directory for background agent tasks.
- Hardened bootstrap_windows.ps1 with explicit watchdog and dependency verification to ensure reliable file sync on Windows.
- Added self-correcting path logic to install_service.py to resolve agent_node package imports.

feat(mesh): autonomous windows provisioning and lifecycle management ...

- Implemented secure self-purge mechanism for agent nodes (purge.py).
- Refactored bootstrap_windows.ps1 for headless/non-interactive installation.
- Added POST /nodes/purge endpoint to Hub for token-based self-deregistration.
- Enhanced Nodes UI with 'Purge & Deregister' option and platform-aware command dispatch.
- Modularized backend services (Mesh, NodeRegistry, Session, Tool, RAG) to centralize business logic.
- Stabilized Windows PTY serialization and terminal output dispatch.
- Added integration tests for node purge flows.

Fix Windows PyWinPTY terminal boundary string drops via bat spool execution and full Windows deployment support