chore: prepare dyns v0.5.0 release

[eareimu]

Summary

• bump dyns to 0.5.0 for the h3x 0.5.0 compatibility line
• update h3x dependency to 0.5.0
• tighten publish workflow checks and avoid --locked because this repo ignores Cargo.lock
• split mDNS query helpers so selector-aware lookups preserve sequence handling

Validation

• cargo +nightly fmt
• cargo test --all-features
• cargo +nightly clippy --all-targets --all-features -- -D warnings
• RUSTUP_TOOLCHAIN=1.93 cargo semver-checks --baseline-version 0.4.0

Release notes

• release tag planned as v0.5.0
• waits for h3x 0.5.0 registry visibility before final publish readiness