build(deps-dev): bump @storybook/theming from 8.6.4 to 8.6.12

Bumps [@storybook/theming](https://github.com/storybookjs/storybook/tree/HEAD/code/lib/theming) from 8.6.4 to 8.6.12.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Commits](https://github.com/storybookjs/storybook/commits/v8.6.12/code/lib/theming)

---
updated-dependencies:
- dependency-name: "@storybook/theming"
  dependency-version: 8.6.12
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -77,7 +77,7 @@
     "@storybook/manager-api": "8.6.4",
     "@storybook/preview-api": "8.6.4",
     "@storybook/test": "8.6.4",
-    "@storybook/theming": "8.6.4",
+    "@storybook/theming": "8.6.12",
     "@storybook/web-components": "8.6.4",
     "@storybook/web-components-vite": "8.6.4",
     "@types/chai": "5.2.0",