Update README badge URLs from Tada5hi/routup to routup/plugins

[tada5hi]

Pre-existing issue surfaced during PR review

Reported in: PR #783, review comment by @coderabbitai[bot] on packages/swagger-ui/README.md
Files: every packages/*/README.md plus the root README.md

Description

All package READMEs (and the root README) reference badge URLs pointing at Tada5hi/routup (the author's personal repo) rather than routup/plugins where the code now lives. The CI / codecov / Snyk badges therefore display stale status from an unrelated repo.

[![main](https://github.com/Tada5hi/routup/actions/workflows/main.yml/badge.svg)](https://github.com/Tada5hi/routup/actions/workflows/main.yml)
[![codecov](https://codecov.io/gh/tada5hi/routup/branch/master/graph/badge.svg?token=QFGCsHRUax)](https://codecov.io/gh/tada5hi/routup)
[![Known Vulnerabilities](https://snyk.io/test/github/Tada5hi/routup/badge.svg)](https://snyk.io/test/github/Tada5hi/routup)

Suggested fix

Sweep all README files and replace the Tada5hi/routup / tada5hi/routup URLs with routup/plugins:

[![main](https://github.com/routup/plugins/actions/workflows/main.yml/badge.svg)](https://github.com/routup/plugins/actions/workflows/main.yml)
[![codecov](https://codecov.io/gh/routup/plugins/branch/master/graph/badge.svg)](https://codecov.io/gh/routup/plugins)
[![Known Vulnerabilities](https://snyk.io/test/github/routup/plugins/badge.svg)](https://snyk.io/test/github/routup/plugins)

Doing this repo-wide in a single PR keeps READMEs consistent — fixing it in only the new packages would diverge from the existing convention.