deploy: add deploy-voip.sh + fix Rust version (use latest)

- scripts/deploy-voip.sh: full Hetzner cx23 + Docker + CF DNS deploy
  --create: provision VPS, install Docker
  --dns: update CF A + AAAA records
  --deploy: upload source, docker compose up
  --test: 6 HTTP checks + TLS + IPv6
  --all: end-to-end in one command
- Dockerfiles: use rust:latest (time crate needs 1.88+)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/deploy/docker/Dockerfile.server

@@ -1,6 +1,6 @@
 # featherChat server — multi-stage build
 # Build context: featherChat repo root (../../..)
-FROM rust:1.85-bookworm AS builder
+FROM rust:latest AS builder
 
 WORKDIR /build