feat(clients): scaffold mobile (Capacitor) + desktop (Electron) shells

Plan + decisions in CLIENTS.md (parallel mobile+desktop; desktop = technician
client + existing remote-control agent host; mobile = Capacitor wrap).

- desktop/: Electron technician client — loads the live Connect UI, native
  screen capture via setDisplayMediaRequestHandler, persisted session, external
  links to browser; electron-builder config for Win/Mac/Linux installers.
- mobile/: Capacitor project — server.url loads Connect UI, push/camera/status-bar
  plugins declared, www splash fallback; iOS/Android added via `cap add`.
- Reuses the existing /api/v1 + Bearer auth backend; no web-code changes.
- .gitignore: ignore generated mobile/android, mobile/ios platform dirs.

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

desktop/README.md

@@ -0,0 +1,26 @@
+# Biz Connect — Desktop client
+
+Electron shell that loads the live Connect web UI and adds native screen capture. See the
+overall plan in [../CLIENTS.md](../CLIENTS.md).
+
+## Run (dev)
+```bash
+npm install
+SERVER_URL=http://localhost:8090 npm start     # default is https://remote.bizgaze.com
+```
+
+## Build installers
+```bash
+npm run dist        # electron-builder → Win NSIS / Mac dmg / Linux AppImage
+```
+Signed, trusted installers need certificates:
+- **Windows:** an EV (or OV) code-signing certificate.
+- **macOS:** Apple Developer ID cert + notarization (`CSC_LINK`, `APPLE_ID`, `APPLE_APP_SPECIFIC_PASSWORD`).
+
+## Notes
+- The window loads `${SERVER_URL}/home`; relative `/api` and `/ws` URLs work because the
+  origin is the server itself — no web-code changes.
+- `setDisplayMediaRequestHandler` in `main.js` is what makes "Share Screen" work in Electron;
+  it currently defaults to the primary display. Swap in a source-picker for production.
+- The session is persisted (`persist:bizconnect`) so login survives restarts.
+- `window.__NATIVE__ === 'desktop'` is exposed for the web UI to feature-detect.