LanExtend v0.2.0: release updates and immersive receiver overlay

[Modole]

Summary

• add a guarded GitHub Releases update check with a fixed official download destination and rate-limit fallback
• hide the Windows receiver video status/control overlay by default; reveal it on pointer, touch, or focus and auto-hide after inactivity
• fix Windows config permission assertions and prevent electron-builder from implicitly publishing in CI
• bump the app to v0.2.0 and document release, update, security, and acceptance behavior

Verification

• npm test — 23/23 passing
• npm run build:native and helper --probe
• macOS Universal DMG/ZIP built and verified; Electron app and helper include x86_64 + arm64
• Windows x64 portable EXE/ZIP built and archive-tested
• receiver GUI visually checked on macOS
• SHA-256 manifest generated for the four release assets

Distribution warning

The v0.2.0 packages are unsigned development-preview builds. The product remains restricted to trusted IPv4 LANs with no device authentication.