Feature request: Support network-accessible URLs for remote/Tailscale sessions

[centdix]

Use case

I run pi on a remote development machine that I access from my laptop over Tailscale. The URL shown by the extension is always something like:

  http://localhost:<port>

That works only from inside the remote machine. From my laptop/browser, I need to open the same server via the machine's Tailscale IP, for example:

  http://100.x.y.z:<port>

Currently I need to manually replace localhost with the Tailscale IP.

Expected behavior

It would be useful if the extension could generate a browser URL that is accessible from another machine.

Possible options:

Option 1: Explicit public base URL

Support an env var like:

  PLANNOTATOR_PUBLIC_URL=http://100.x.y.z:19432

Then Plannotator would display/open:

  http://100.x.y.z:19432

instead of:

  http://localhost:19432

Option 2: Auto-detect network IPs in remote mode

When PLANNOTATOR_REMOTE=1, optionally include candidate URLs from non-loopback interfaces, e.g.:

  Remote session. Open Plannotator at one of:
  - http://100.x.y.z:19432
  - http://192.168.x.y:19432
  - http://localhost:19432