v1.5.1 Release Spark cart page fix

[next-devin]

Release Spark 1.5.1 so new installations can receive the cart page fix from #75. Update the manifest and both documented version markers, and move the existing Unreleased notes into the dated release section.

Includes the cart quantity, subscription frequency and Remove fix, plus the contract scope and live-check corrections from #71–#73. Runtime code and compiled CSS are unchanged by this release PR.

Validation: all three version markers agree on 1.5.1 and the dated changelog is present; git diff --check passes. The cart fix passed 145 local tests and CI in #75. This PR's CI checks the release commit.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Release commit 6d032e57 is a clean version bump. All three documented version markers agree on 1.5.1:

• manifest.json:3 -> 1.5.1
• CLAUDE.md:6 -> 1.5.1
• README.md:5 -> 1.5.1

The dated ## 1.5.1 - 2026-10-04 header in CHANGELOG.md:11 is correctly inserted, and the previously-Unreleased bullets (theme-contract scope, live-check validation, cart formset fix) have moved under it as the PR description states. The empty ## Unreleased section above is preserved per the repo's existing convention (it was already empty in the prior commit). No runtime code, templates, or compiled CSS touched, matching the "runtime code and compiled CSS are unchanged" claim.

Files Reviewed (4 files)

• CHANGELOG.md
• CLAUDE.md
• README.md
• manifest.json

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