security: harden protocol parsing and resource limits

[zytakeshi]

Summary

• Harden protocol parsers and authentication paths across ShadowTLS, Hysteria2, TUIC, VLESS, VMess, XUDP, WebSocket, AnyTLS, REALITY, SOCKS, HTTP, and Shadowsocks.
• Add bounded resource caches/session tables, replay/nonce protections, release-mode bounds checks, and config/debug redaction.
• Bump package version to 0.2.9 and add direct zeroize dependency for REALITY secret cleanup.

Changes

• Protocol parsing: guard short/truncated frames, padding underflow, VMess AEAD header length, TUIC/Hysteria2 datagrams, VLESS varints, ShadowTLS zero-payload frames, WebSocket control frames.
• Crypto/auth: constant-time comparisons, VMess auth-ID replay cache, VMess nonce exhaustion error, REALITY key zeroization and generic auth failure logs.
• Resource limits: bounded DNS caches, worker queues, AnyTLS streams, TUIC/Hysteria2 UDP sessions, XUDP sessions, and TUIC fragment reassembly.
• Runtime hardening: FFI startup defaults, write_all WriteZero handling, SlideBuffer release asserts, hot-reload error handling, and redacted config Debug output.

Verification

• cargo fmt --all --check
• git diff --check
• cargo check --locked --lib
• cargo test --locked --lib
• cargo test --locked --bins
• cargo test --locked --release --lib vmess::vmess_stream::tests::test_try_decrypt_rejects_padding_larger_than_data_len
• cargo test --locked --release --lib xudp::message_stream::tests::skips_many_empty_frames_without_recursing
• cargo check --locked --target aarch64-apple-ios --features ffi --lib

Notes

• Existing warnings remain for unused interface variables in socket_util.rs and Rust 2024 unsafe-op warnings in ffi/ios.rs; they do not fail the checked builds.
• This PR branch also includes the existing local SS2022 clock-skew commit already ahead of upstream.