feat: add TLS and optional mTLS support for Docker socket proxy

[pipethedev]

feat: add TLS and optional mTLS support for Docker socket proxy

• add TLS-aware bind generation in entrypoint (default 2376 when TLS=1)
• support optional client cert verification via TLS_VERIFY_CLIENT + CA path
• add TLS-related env defaults and expose port 2376
• extend test harness for custom port/mount/env and add TLS + mTLS tests
• generate test certs at runtime (no committed cert artifacts)
• document TLS/mTLS usage and bind/TLS environment variables
• ignore local test cert material in .gitignore