chore(deps): update rust crate handlebars to v6.4.2

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
handlebars	workspace.dependencies	patch	6.4.1 → 6.4.2

---

Release Notes

sunng87/handlebars-rust (handlebars)

v6.4.2

Compare Source

• [Fixed] Access to local variables like @key, @index, etc. in #with and
  partial block [#​758]
• [Fixed] Preserve ordering when iterating an array context inside a partial
  that receives hash parameters [#​760]
• [Changed] Enable serde_json preserve_order feature. JSON objects are now
  iterated in insertion order (matching Handlebars.js semantics) instead of
  alphabetical key order. This fixes index-key ordering for array contexts
  converted into objects by partial hash parameters (e.g. "10" no longer
  sorts before "2").

---

Configuration

📅 Schedule: (UTC)

• Branch creation
  • At any time (no schedule defined)
• Automerge
  • At any time (no schedule defined)

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.

[rajpratham1]

This is a standard dependency update generated by Renovate. The PR only bumps handlebars from 6.4.1 to 6.4.2 in Cargo.lock and updates the corresponding checksum, with no application code changes. Since all GitHub checks are passing, this looks safe to merge.