v3.1.0 — AIGATE_TOKEN master auth + talkies network fix + dead-var cleanup

Single AIGATE_TOKEN now defaults every aigate-owned service's bearer
(LiteLLM, claudebox, pibox-zai, predictalot, mcp, telethon,
stealthy-auto-browse, hybrids3). Per-service tokens still override.
Backwards compatible — existing .env files keep working unchanged.

Also: talkies + talkies-cuda now on `aigate-public` so their HF
prefetch at boot can resolve huggingface.co (was failing on the
internal-only network). Dead TALKIES_PREFETCH env passthrough (never
read by upstream psyb0t/talkies) stripped.

See CHANGELOG.md for full details.