fix: preserve nested structured values on repeated saves

[bobbwal]

Description

Fixes nested structured field re-serialization in the admin form so block object values (for example Hero CTA config) are preserved across subsequent unrelated saves.

Fixes #648

Changes

• Updated structured value reading in packages/core/src/templates/components/dynamic-field.template.ts to compute object/array values from live structured subfields recursively, instead of relying on stale hidden JSON.
• Kept hidden-input parsing as a fallback only when structured containers are not present.
• Rebuilt core output (packages/core/dist/*) and regenerated packages/core/src/db/migrations-bundle.ts.

Testing

• Manual reproduction and verification:
  1. Set Hero CTA styles/fields (including secondary) and save.
  2. Reopen, make unrelated change, save again.
  3. Confirm nested CTA values persist.
• npx playwright test tests/e2e/54-hero-cta-style-persistence.spec.ts --config tests/playwright.config.ts

Unit Tests

• Added/updated unit tests
• All unit tests passing

E2E Tests

• Added/updated E2E tests
• All E2E tests passing

Checklist

• Code follows project conventions
• Tests added/updated and passing (manual + local targeted validation)
• Type checking passes
• No console errors or warnings
• Documentation updated (if needed)