Add Python agent, WebSocket relay, real viewer, enrollment tokens

- WebSocket relay service (FastAPI) bridges agents and viewers
- Python agent with screen capture (mss), input control (pynput),
  script execution, and auto-reconnect
- Windows service wrapper, PyInstaller spec, NSIS installer for
  silent mass deployment (RemoteLink-Setup.exe /S /SERVER= /ENROLL=)
- Enrollment token system: admin generates tokens, agents self-register
- Real WebSocket viewer replaces simulated canvas
- Linux agent binary served from /downloads/remotelink-agent-linux
- DB migration 0002: viewer_token on sessions, enrollment_tokens table
- Sign-up pages cleaned up (invite-only redirect)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agent/build.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# Build script for RemoteLink Agent
+# Run on the target platform (Windows/macOS/Linux)
+#
+# Requirements: Python 3.11+, pip, pyinstaller, (Windows) NSIS
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+cd "$SCRIPT_DIR"
+
+echo "==> Installing dependencies…"
+pip install -r requirements.txt
+pip install pyinstaller
+
+echo "==> Building with PyInstaller…"
+pyinstaller agent.spec --clean --noconfirm
+
+echo "==> Portable binary: dist/remotelink-agent"
+ls -lh dist/remotelink-agent* 2>/dev/null || ls -lh dist/
+
+# Windows: build NSIS installer
+if [[ "$OSTYPE" == "msys"* ]] || [[ "$OS" == "Windows_NT" ]]; then
+  if command -v makensis &>/dev/null; then
+    echo "==> Building NSIS installer…"
+    makensis installer.nsi
+    echo "==> Installer: RemoteLink-Setup.exe"
+  else
+    echo "==> NSIS not found — skipping installer build."
+    echo "    Download NSIS from https://nsis.sourceforge.io"
+  fi
+fi
+
+echo "==> Done."