Add rewrite-headers plugin

[pinetops]

Summary

• Adds the traefik-plugin-rewrite-headers plugin to the traefik config
• Enables per-service Host header rewriting via Docker labels
• Useful for projects that need a canonical hostname regardless of access method (e.g. *.localhost rewritten to *.u2i.me for Cloudflare tunnel parity)

Example usage (in a project's compose labels)

labels:
  - "traefik.http.routers.myapp.middlewares=myapp-rewrite-host"
  - "traefik.http.middlewares.myapp-rewrite-host.plugin.rewriteheaders.rewrites[0].header=Host"
  - "traefik.http.middlewares.myapp-rewrite-host.plugin.rewriteheaders.rewrites[0].regex=myapp\\.localhost"
  - "traefik.http.middlewares.myapp-rewrite-host.plugin.rewriteheaders.rewrites[0].replacement=myapp.tom.u2i.me"

Test plan

• Run traefik-dev-proxy restart (or reinstall) and verify traefik starts without errors
• Verify existing services without the middleware continue to work unchanged

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