Phase 2: Add platform, channels, core_version to virtual emulator and OTA endpoint

Add virtual device emulator (Flask) for relay and button types ...

- New tools/virtual_devices/ with Flask emulator, CLI, and web UI
- Supports relay (4 ch, set_state) and button (4 ch, click events)
- CLI: create, start, stop, list, status, click, remove, register
- Emulates full device REST contract: /about, /status, /action, /set_token, /reset, /channels_schema
- Web UI for visual control and monitoring
- Integrate with server registration via /api/v1/devices/setup/new-device
- Allow IP:port in setup_new_device validation for virtual devs

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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