[feat] Enable Assets sidebar in production (#6717)

## Summary
- Removed development-only restriction for Assets sidebar tab
- Assets sidebar is now available in all environments (production and
development)

## Changes
- Removed `import.meta.env.DEV` condition check in
`registerCoreSidebarTabs()`
- Removed outdated comment about development-only display

## Test plan
- [ ] Verify Assets sidebar appears in production build
- [ ] Verify Assets sidebar functionality works correctly in production

🤖 Generated with [Claude Code](https://claude.com/claude-code)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6717-feat-Enable-Assets-sidebar-in-production-2ae6d73d36508157a7e1d4eb9cbf0a42)
by [Unito](https://www.unito.io)

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Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: github-actions <github-actions@github.com>

Author: 3 people