Deploy the new register.py to the server (copy button is not live yet)

The branded token page, the Copy button and the link back to the instructions site are all in main (d7636dd) but the California server is still running the old register.py. Until it is redeployed, someone following the new site through step 1 lands on the old bare token page — which has no copy button and links to github.com, the exact thing we just moved people away from.

Follow server/SETUP.md as usual, plus one new setting:

# /etc/langtechdepot/register.env
SITE_URL=https://sillsdev.github.io/langtechdepot

Without it the service falls back to that same default, so the deploy is not broken if it is forgotten — but it is the one line to change when the site moves to its own name (#13).

Then check:

• https://depot.langtech.cloud/ shows the restyled form
• https://depot.langtech.cloud/signup?os=windows shows the same form (a second address for it, reserved for after the merge — the site links to /)
• a real registration shows the token with a working Copy button
• the Next: download the installer button lands on windows.html, not index.html
• the token email carries the instructions link

python3 server/test_register.py covers all of this against a stub Syncthing and passes 25/25, so a failure here is an environment problem rather than a code one.

Start with server/SETUP.md and run python3 server/test_register.py to confirm the application checks pass against the stub Syncthing. Deploy the current server/register.py to the California server and set SITE_URL in /etc/langtechdepot/register.env. Verify the root and signup URLs, the Copy button, the installer link, and the instructions link in registration email.