Remove content migrated to CLI

[chocolatkey]

Also, prepare CHANGELOG

[mickael-menu]

Just a typo in the Markdowns. I bet Copilot would have spotted it, let's see.

EDIT: Nope, disappointed ☹️

[Copilot]

Pull Request Overview

This PR removes legacy server and client code that has now been migrated to the new CLI repository and updates the documentation accordingly.

• Removed the entire contents of the "cmd/rwp" command, including server routes, client HTTP handlers, caching modules, and supporting helper functions.
• Updated README and CHANGELOG to point users to the new Readium CLI repository and reflect the changes in the project’s functionality.

Reviewed Changes

Copilot reviewed 21 out of 25 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
cmd/rwp/cmd/serve/*	Removed server routing and debugging endpoints.
cmd/rwp/cmd/serve/client/*	Removed HTTP client, IP address and authentication helpers.
cmd/rwp/cmd/serve/cache/*	Removed caching mechanisms for publications.
cmd/rwp/cmd/serve/api.go, serve.go, etc.	Removed legacy API endpoints and server bootstrapping code.
cmd/rwp/cmd/root.go, manifest.go, helpers	Removed CLI command definitions and related helper functions.
README.md	Updated to direct users to the new Readium CLI repository.
CHANGELOG.md	Updated changelog entries to document the removals and new features.

Files not reviewed (4)

• .github/workflows/release.yml: Language not supported
• .goreleaser.yaml: Language not supported
• Dockerfile: Language not supported
• Makefile: Language not supported

Comments suppressed due to low confidence (2)

README.md:3

• The updated README directs users to the new CLI repository. Consider ensuring that all references and links are consistently updated across the project documentation.

+**Looking for the `rwp` command-line tools? Checkout the new [https://github.com/readium/cli](Readium CLI) repo!**

CHANGELOG.md:9

• The changelog entry clearly outlines the removed components and new features; verify that dependent documentation or integration references are also updated to reflect the migration to the CLI.

+### Removed