[Plugin] Smartcard plugin — Workstation Agent

[maxzaikin]

Summary

Implement VaultFlower.Agent.Workstation Windows Service.
Reads Mifare NFC card UID from USB NFC reader and
exposes it via localhost WebSocket to the browser.

Context

See Plugin-Smartcard — Workstation Agent section and
Architecture-Container-Architecture

Acceptance Criteria

• .NET 9 Windows Service project
• NFC reader access via PC/SC (WinSCard API)
• Polls for card presence every 200ms
• WebSocket server on localhost:7777 (loopback ONLY — never 0.0.0.0)
• CORS: AllowedOrigins = ["https://vfw-core.contoso.com"] only
• On card detected: sends JSON { "uid": "A1B2C3D4", "card_type": "MIFARE_DESFIRE" }
• On card removed: sends JSON { "uid": null }
• No persistence — UID only in memory, never written to disk or log
• Service auto-starts on Windows boot
• Works without admin rights after initial installation
• Installer (MSI or Setup.exe) for GPO deployment
• Supports: ACS ACR122U, ACS ACR1252U, HID OMNIKEY 5022
• Unit tests for WebSocket message format