Add basic docs page

[keenanjohnson]

No description provided.

[Copilot]

Pull request overview

This PR adds a hosted, interactive API reference (Scalar UI) backed by an OpenAPI 3.1 spec embedded into the binary. It also reworks the README to point users at the live docs and adds a lightweight docs subcommand for previewing the docs locally without needing InfluxDB or the API key store.

Changes:

• New internal/docs package that embeds openapi.yaml and serves it along with a Scalar-rendered HTML reference at /openapi.yaml and /docs.
• main.go registers the new doc routes on the main server and adds a docs subcommand that runs a minimal docs-only server.
• README is rewritten to link to the hosted docs, document rate limits, the new /healthz and /docs endpoints, and the docs update workflow.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
README.md	Replaces inline endpoint docs with links to /docs, adds rate-limit and docs-preview sections, updates run command to go run ..
main.go	Wires /docs and /openapi.yaml into the server and adds a docs subcommand for a docs-only preview.
internal/docs/docs.go	New package: embeds the spec and serves the Scalar reference HTML.
internal/docs/openapi.yaml	New OpenAPI 3.1 spec describing all endpoints, schemas, auth, and error responses.

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