No-DB build: remove the registration UI completely (build-aware)

In a no-database (guest-mode) build registration is non-functional
(yc_register's body is #ifdef DATABASE), so the password field, the
'Register' link and register.html are misleading. Remove them for the
no-DB build while keeping the full login page for a future DB build:

- html/index.html: restored to the full login (password field + Register
  link) - used by a DB build.
- html/index_guest.html: new guest login page - no password field, no
  Register link, a 'guest mode, no password needed' note.
- Dockerfile (no-DB build): serve index_guest.html as httpd.startsite, and
  drop register.html and yc_register.so from the image (the module preload
  scans the dir, so a missing .so is simply not loaded; an on-demand
  get_module for the register event fails gracefully -> no-op).

Verified: start page is index_guest.html (no password/register);
register.html -> 'Page not found'; yc_register.so absent from the image;
normal login + multi-user chat still work.

0 files changed, 0 insertions, 0 deletions