Add explicit HTTPS proxy egress

[kcosr]

Summary

• add explicit HTTPS proxy listener support and HTTPS parent-proxy egress configuration
• harden listener lifecycle, graceful shutdown draining, and related validation/tests
• document linux-arm64 release archives and remove stale committed build-service endpoint from repo config

Validation

• BUILD_SERVICE_ENABLED=true BUILD_SERVICE_ENDPOINT=http://pc:6680 BUILD_SERVICE_WORKSPACE_TTL=86400 build-cli build cargo -- +stable fmt --check