Use DapNET API definition as "single source of truth"

[Trayshar]

Use dapnet-core/api-docs as "single source of truth". All routes, data definitions and validation rules are to be generated automatically from them.

Reasoning: The API surface of this project is rather large and especially the validation rules for input forms are complex. Managing this complexity on the server, the client(s) and the API document is unpromising and will lead to poor maintainability.

• API routes: Replace src/api/api_routes.ts with auto-generated code, see openapi-typescript for a potential solution.
• Form validation: Find a way to convert OpenAPI validation rules into Quasar validation rules.
• Update the API to actually match our backend... or vice-versa