FX.25 Website: show/hide eye on password fields (sign in, create account)

Password fields had no way to check what was typed. /login, /signup and /admin/login now have an eye button inside the field that shows or hides the password. Because it lives in the shared account/field.inc, the reset-password page, the password fields on the profile page and the app sign-in confirm page get it too. The button appears only once site.js runs (no dead button without JavaScript); the field goes back to masked on submit so browsers still offer to save it as a password; Edge's own eye is hidden so there are not two. Tested in headless Chromium on /login, /signup and /admin/login (reveal, re-mask, masked on submit, no JavaScript). Not tried on the other pages, in Edge or Safari, or with a screen reader. Not added to the cloud encryption passphrase, own-storage secret or SSO secret fields, which do not use field.inc.