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/remotelink-agent.spec

@@ -0,0 +1,42 @@
+# -*- mode: python ; coding: utf-8 -*-
+from PyInstaller.utils.hooks import collect_data_files
+
+datas = []
+datas += collect_data_files('mss')
+
+
+a = Analysis(
+    ['agent.py'],
+    pathex=[],
+    binaries=[],
+    datas=datas,
+    hiddenimports=['mss', 'mss.linux', 'PIL', 'PIL.Image', 'PIL.JpegImagePlugin', 'pynput', 'pynput.mouse', 'pynput.keyboard', 'websockets', 'websockets.legacy', 'websockets.legacy.client', 'httpx', 'httpcore'],
+    hookspath=[],
+    hooksconfig={},
+    runtime_hooks=[],
+    excludes=[],
+    noarchive=False,
+    optimize=0,
+)
+pyz = PYZ(a.pure)
+
+exe = EXE(
+    pyz,
+    a.scripts,
+    a.binaries,
+    a.datas,
+    [],
+    name='remotelink-agent',
+    debug=False,
+    bootloader_ignore_signals=False,
+    strip=False,
+    upx=True,
+    upx_exclude=[],
+    runtime_tmpdir=None,
+    console=True,
+    disable_windowed_traceback=False,
+    argv_emulation=False,
+    target_arch=None,
+    codesign_identity=None,
+    entitlements_file=None,
+)