Improve DAG toggle contrast in dark mode

[bobu-putheeckal]

What

Improve dark-mode switch contrast by adding a dark-mode border to the shared Chakra switch control. The checked state keeps using the existing color palette token, while the unchecked/off state gains a visible outline on dark surfaces.

This addresses the DAG pause toggle contrast reported in #66759.

Why

In dark mode, the unchecked switch track can blend into the surrounding dark background, making paused/off DAG toggles hard to distinguish. A token-based border makes the switch shape clearer without introducing new colors or changing light-mode behavior.

Tests

• pnpm exec eslint src/theme.ts
• pnpm exec tsc --p tsconfig.app.json --pretty false
• pnpm build

Screenshots

I could not capture a full Airflow DAG-list screenshot from the raw Vite dev shell because that shell depends on Airflow backend-provided base/config values to render the app. The change is limited to the theme recipe and was verified with the focused static checks and production build above.

---

closes: #66759

Was generative AI tooling used to co-author this PR?

• Yes — OpenAI Codex

Generated-by: OpenAI Codex following the guidelines

[bobu-putheeckal]

Additional detail: the visual change is isolated to the shared Chakra switch recipe in dark mode. Unchecked DAG toggles now get a token-based border (border.emphasized) so the switch outline remains visible against the dark table background, while light mode keeps the transparent border and checked switches keep the color-palette border.

[kaxil]

PR template hasn't been followed on any of your PRs. As such I am closing all your PRs since I see little to no evidence of actual testing and mass PRs to Airflow & other repos.