chore: Prepare release 2.1.0

[mparticle-automation]

Preparing for release 2.1.0

• Updated pubspec.yaml to new version
• Updated CHANGELOG.md
• Updated VERSION file
• Ran a dry-run publish

[cursor]

PR Summary

Low Risk
Low risk: release bookkeeping and dependency lockfile updates only; no runtime code changes.

Overview
Prepares the 2.1.0 release by bumping the package version in pubspec.yaml/VERSION and adding a new 2.1.0 entry to CHANGELOG.md (CNAME routing init examples + native dependency version pins/bumps).

Updates release links in the changelog and refreshes pubspec.lock (including SDK constraints recorded in the lockfile) from a publish dry-run.

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