docs(changelog): add new entries from changelog

[windmill-internal-app]

This PR adds new changelog entries.

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Summary by cubic

Adds a new sidebar changelog entry for "Scheduled Ducklake maintenance" dated 2026-07-04, linking to the detail page so users can quickly find the maintenance notice.

^{Written for commit 423641c. Summary will update on new commits.}

[cloudflare-workers-and-pages]

Deploying windmill with    Cloudflare Pages

Latest commit:	423641c
Status:	✅  Deploy successful!
Preview URL:	https://7976f17d.windmill.pages.dev
Branch Preview URL:	https://changelog-update-28736388799.windmill.pages.dev

View logs

[github-actions]

Pi Review

Good to merge

A single new changelog entry added to frontend/src/lib/components/sidebar/changelogs.ts — well-formed, matches the Changelog type, and correctly placed at the top of the array (newest-first). No code logic changes, no public surfaces affected.

Test coverage

CI / workflows / docs / config-only change — no automated tests expected. No manual verification needed.

[github-actions]

Codex Review

cc @windmill-internal-app[bot]
Mergeable, but should ideally address nits: broken changelog link

Found 1 issue:

1. [P2] The newly added changelog entry points to a URL that currently returns 404 on a normal GET request. SidebarContent.svelte renders changelog.href directly as the external menu link, so users clicking “Scheduled Ducklake maintenance” from the sidebar will land on a missing page unless the slug is corrected or the page is published.
   frontend/src/lib/components/sidebar/changelogs.ts:10

Test coverage

Frontend data-only change; no automated tests are expected for this changelog list. Manual verification should confirm the added sidebar changelog link opens the intended Windmill changelog page successfully.