docs: add missing port mapping to minimal redis-proxy docker run example

[Copilot]

The "Minimal (redis-only)" docker run example omitted -p 6379:6379, making the proxy unreachable from the host in a typical local setup.

Change

• Added -p 6379:6379 to the minimal docker run snippet in docs/redis-proxy-deployment.md

docker run --rm \
  -p 6379:6379 \
  ghcr.io/bootjp/elastickv/redis-proxy:latest \
  -listen :6379 \
  -primary redis.internal:6379 \
  -mode redis-only

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