feat: add Android remote gameplay client

[b31o8321]

Summary

• add opt-in Mac LAN remote access with pairing, device control, and explicit route policy
• add idempotent replayable turn runs for disconnect-safe gameplay
• add Flutter Android discovery, pairing, session hydration, and reconnectable gameplay UI
• add Android CI and unsigned/internal artifact boundaries

Verified locally

• backend remote auth and turn-run tests: 33 passed
• Vue tests: 9 passed; production build passed
• Flutter analyze passed; 43 tests passed
• debug APK, unsigned release APK, and unsigned release AAB builds passed

Release blockers still open

• packaged Mac + physical Android acceptance
• approval/QR/PIN and DHCP/mDNS validation on real home routers
• 30-turn huihui-ai_qwen3-14b-abliterated playtest and 100-turn disconnect soak
• signed internal RC, security review, performance measurements, and final maturity score