Add API Reference

[AHGIJMKLKKZNPJKQR]

Description

Long awaited API viewer, using Scalar docusaurus plugin.
The API reference isn't versioned, since there is only 1 version of the HTTP API

[linear]

FCE-3047 API reference viewer in docs

[Copilot]

Pull request overview

Adds an unversioned “API Reference” section to the Docusaurus site using the Scalar plugin, and updates docs to include uv installation instructions.

Changes:

• Integrate @scalar/docusaurus and add a top-level navbar link to /api/rest.
• Hide the docs version dropdown when viewing the unversioned API reference.
• Update backend docs (current + versioned) to add uv tabs and normalize tab labels.

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
yarn.lock	Locks new Scalar + transitive dependencies.
package.json	Adds Scalar plugin (and @docusaurus/utils) dependencies.
docusaurus.config.ts	Configures Scalar plugin route and adds “Docs”/“API Reference” navbar items.
src/theme/NavbarItem/index.tsx	Wraps navbar items to hide the version dropdown on the API reference route.
src/css/custom.css	Tweaks Scalar page typography/badges to better match site styling.
docs/api/reference.md	Updates reference page to link to the new REST API reference route.
docs/how-to/backend/server-setup.mdx	Normalizes package-manager tab labels and adds uv install instructions.
docs/tutorials/backend-quick-start.mdx	Adds uv install instructions for Python dependencies.
versioned_docs/version-0.24.0/tutorials/backend-quick-start.mdx	Adds uv install instructions (v0.24.0).
versioned_docs/version-0.24.0/how-to/backend/server-setup.mdx	Normalizes tab labels + adds uv (v0.24.0).
versioned_docs/version-0.25.0/tutorials/backend-quick-start.mdx	Adds uv install instructions (v0.25.0).
versioned_docs/version-0.25.0/how-to/backend/server-setup.mdx	Normalizes tab labels + adds uv (v0.25.0).
versioned_docs/version-0.26.0/tutorials/backend-quick-start.mdx	Adds uv install instructions (v0.26.0).
versioned_docs/version-0.26.0/how-to/backend/server-setup.mdx	Normalizes tab labels + adds uv (v0.26.0).

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