fix: resolve P2P data plane decrypt failure and improve test environment

- Fix key derivation in both sdk/agent.go and internal/vl1/noise.go:
  sort public keys before hashing, use shared key for send/recv
- Adjust docker-compose port mappings to 7150-7153 range (within 7000-7200)
- Add GOPROXY env to Dockerfiles for Go module download in restricted networks
- Verified: all 3 clients connect with 2 peers each, zero decrypt errors

Dockerfile.server

@@ -1,4 +1,5 @@
 FROM golang:1.26-alpine AS builder
+ENV GOPROXY=https://goproxy.cn,https://goproxy.io,direct
 RUN apk add --no-cache gcc musl-dev
 WORKDIR /src
 COPY . .