fix(docker): use Rust nightly for edition2024 support

- Change FROM rust:1.84-slim to rustlang/rust:nightly-slim
- Fixes Docker build failure: 'edition2024 feature is not stabilized'
- Enables successful build of rmcp-macros-0.3.2 dependency requiring edition2024
- Local Docker test confirms successful build and binary execution
- Resolves final blocker for Docker image creation in release workflow

closes #docker-edition2024-nightly-support

Author: milliondreams

Dockerfile

@@ -2,7 +2,7 @@
 # Supports both source builds (CI) and crates.io installs (releases)
 
 # Build stage
-FROM rust:1.82-slim AS builder
+FROM rustlang/rust:nightly-slim AS builder
 
 # Install system dependencies for building
 RUN apt-get update && apt-get install -y \