Add .http request files to Minimal API and Web API #80

Visual Studio, Rider and VS Code can run requests from a .http file in one click, and the Microsoft templates ship one. GraphQL, MCP and Lambda Function already have Nitro, the Inspector and the emulator, so this only covers the two HTTP templates.

Phase 1: The files

• src/Presentation/Presentation.http in CleanMinimalApi with a request for every endpoint, including a search and a failing validation
• The same in CleanWebApi
• A bearer token variable that stays commented out unless --include-auth is on

Phase 2: Docs

• Mention it in RUN.md, the run-locally pages and the expose-a-use-case skill (add a request when you add an endpoint)

Checks: the build pipeline passes, and every request in the file works against docker compose up.