Pi-hole, Copyparty, Node-RED: fix web interface access through Tailscale Serve

[jackspiering]

Description

Three stacks could not serve their web interface through Tailscale Serve. Each fix is one value.

• Pi-hole (compose.yaml): Serve forwarded / to http://127.0.0.1:80/admin. Pi-hole redirects to /admin/login, which Serve then forwarded to /admin/admin/login, so the browser looped until it gave up. Serve now forwards to http://127.0.0.1:80, and the web interface is at https://pihole.<tailnet>.ts.net/admin. The root path / answers 403, which is Pi-hole's own behaviour.
• Copyparty (compose.yaml): the built-in config served /data, but the stack mounts the shared folder at /w. Copyparty logged filesystem-path did not exist: '/data' and showed nothing. The config now serves /w.
• Node-RED (compose.yaml, .env): Serve forwarded to port 1080, but Node-RED listens on 1880, so the Tailnet address answered 502. Serve now forwards to 1880, and SERVICEPORT has the same value, so the optional ports block maps the right port as well.

Related Issues

• None.

Verification

Each stack ran from a scratch copy, joined to the Tailnet, first with the files from main and then with this branch. The requests went to https://<name>.<tailnet>.ts.net through Tailscale Serve. They were sent from inside the network of the stack, because the Tailnet policy of the test nodes blocks the Docker host.

Pi-hole (pihole/pihole, Pi-hole 6)

Request	main	This branch
/	302 to /admin/login, then a redirect loop (curl: maximum of 50 redirects)	403
/admin	part of the loop	308 to /admin/, 302 to /admin/login, 200 (login page)
Stylesheet from the login page	404	200

Copyparty (copyparty/ac, Copyparty 1.20.25), with a test folder that holds probe.txt

Check	main	This branch
Log at start	filesystem-path did not exist: '/data'	no such warning
List / as admin	404	200, shows probe.txt, permissions read, write, get
Upload a file as admin	403	201, file is in the host folder
List / without login	empty	empty

Node-RED (nodered/node-red, Node-RED 5.0.7)

Check	main	This branch
Port that Node-RED listens on	1880	1880
Serve target	127.0.0.1:1080	127.0.0.1:1880
https://<name>.<tailnet>.ts.net/	502	200

• docker compose config --quiet in services/pihole, services/copyparty, and services/nodered: passed.
• git diff --check: passed.

Checklist

• I have performed a self-review of my code and followed the templates structure.
• I have added verification that the stack works as expected.
• I have updated necessary documentation (e.g. frontpage README.md ).
• I have selected the correct label(s) for this PR.

Additional Context

• The READMEs of these three services are rewritten in All services: standardize the service READMEs #363, which describes the fixed behaviour. Merge this pull request first.
• Copyparty still logs that it cannot store its runtime config in /cfg, because the stack shares the root-owned ./config folder with Tailscale. It then disables sessions. This pull request does not change that.