[Privacy] Bundle optional embedded Tor runtime

[shadowbipnode]

Research and implement optional embedded Tor runtime support.

Goals:

• ship or bootstrap Tor runtime per platform where legally/distributably feasible
• avoid requiring users to install Tor manually
• start/stop Tor from Zap Browser
• expose clear Tor connection status
• route browser traffic through local Tor SOCKS proxy
• detect Tor bootstrap errors
• document threat model clearly

Important:
Zap Browser should not claim Tor Browser-level anonymity until full isolation/fingerprinting protections are implemented.