Release v1.4.0: mobile video upload and remote control

[amariichi]

Summary

• add a compact mobile upload and playback remote for iPhone, iPad, and Android-class browsers
• let the desktop viewer attach automatically and keep SBS, Looking Glass, and WebXR rendering on the PC
• synchronize play, pause, seek, session replacement, and playback-end reset between phone and desktop
• prepare an on-demand H.264 browser copy for unsupported MOV/HEVC playback while depth inference keeps the original source
• add trusted-LAN and private Tailscale Serve setup instructions
• bump the project and web app to v1.4.0

Validation

• Python: 58 tests passed with dev + inference dependencies
• Frontend: 135 tests passed across 16 files
• Ruff, Python compileall, ESLint, TypeScript, Vite production build, shell syntax, lockfile, and diff checks passed
• iPhone upload, desktop playback/seek synchronization, and Looking Glass output verified on the working setup
• Android hardware was not available for a physical check

Privacy and release safety

• staged only the 35 explicitly reviewed source, test, documentation, and lock files
• no media, model, binary, credential, private key, email address, personal path, machine name, or real LAN/tailnet identifier is included
• the Python backend remains loopback-only; LAN/Tailscale access is routed through the frontend proxy