[Feature] Add Schemas to API

[svenvg93]

📃 Description

This PR adds comprehensive OpenAPI Schema definitions for our API endpoints, to enrich the generated openapi.json used for documentation.

📖 Documentation

I will update the public docs after this merges, so the new openapi.json (with all the added schemas) can be loaded and published.

🪵 Changelog

➕ Added

• ForbiddenError, NotFoundError, UnauthenticatedError, and ValidationError for all the errors.
• ServersCollectionSchema for server list
• ResultsCollectionSchema referencing the existing Result schema, with inline pagination links and meta
• QueuedResultResponseSchema representing a queued test payload and its message
• SpeedtestResultSchema for the full speedtest result structure (all nested objects inlined)
• OpenApiDefinition For all the Definitions
• Groups the Endpoints with tags.
• Add the operationId

📷 Screenshots

No UI changes in this PR.