feat: use Newt in dev-env

[anmazzotti]

What this PR does / why we need it:
Fix #2283

This PR replaces ngrok with newt.
Changes:

• fix: Rancher uses Gitea's ClusterIP to fetch system-charts without going through the internet
• fix: Rancher is immediately configured with the correct CATTLE_CHART_* variables, this prevents a Rancher pod restart and makes the deployment more production-like
• new: Ngrok replaced with Newt
• fix: quickstart script is dropped due to lack of maintenance and validation (documentation has been dropped already since v0.25, no changes needed)
• the kind management environment type has been removed due to lack of usage and maintenance

Usage:

PANGOLIN_ENDPOINT=my.pangolin.example.com \
NEWT_SITE_ID=my-newt-client-id \
NEWT_SITE_SECRET=my-newt-client-secret \ 
PANGOLIN_SITE_DOMAIN=myself.myteam.my.pangolin.example.com \
PANGOLIN_SITE_IDENTIFIER=some-random-identifier \
make dev-env

About NetworkPolicy:

This is a requirement of the RFD.
In this context it's a bit overkill, because the newt pod can't escape the kind container and it's just a dev environment. Right now this does not seem to cause any critical errors in newt.
There's a 10 seconds timeout during boot, but it's not critical.
See newt logs:

INFO: 2026/04/23 08:09:09 Newt version 1.11.0
ERROR: 2026/04/23 08:09:19 Error checking for updates: failed to fetch release info: Get "https://api.github.com/repos/fosrl/newt/releases/latest": context deadline exceeded (Client.Timeout exceeded while awaiting headers)

INFO: 2026/04/23 08:09:19 Config file does not exist at /.config/newt-client/config.json, will create it

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Checklist:

• squashed commits into logical changes
• includes documentation
• adds unit tests
• adds or updates e2e tests

[anmazzotti]

Blocked waiting for a Pangolin instance to be used.

[anmazzotti]

Blocked waiting for EDR approval.