fix: Use rust:latest for time crate MSRV 1.88

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -1,7 +1,7 @@
 # Stage 1: Build patched Rust FFI with HKDF support for Element Call E2EE
 # Fork: onestacked/livekit-rust-sdks branch EC-compat-changes
 # PR: https://github.com/livekit/rust-sdks/pull/904
-FROM rust:1.85-slim-bookworm AS rust-build
+FROM rust:latest AS rust-build
 RUN apt-get update && apt-get install -y --no-install-recommends \
     git cmake g++ libssl-dev pkg-config protobuf-compiler \
     && rm -rf /var/lib/apt/lists/*