Add a footer, move GitHub link out of the nav (#130)

proxy had no page footer at all — no copyright, no license link, no
build/version info — unlike sso-manager-node, which already had one
(now cleaned up in a matching change there). Bring the two in line:

- Added a footer to bottom.ejs: theta42 logo/link, "© <year> theta42"
  with an MIT License link, a GitHub link, and build version/hash.
- Moved the GitHub icon link out of the top nav (where it competed
  with actual navigation items) and into the new footer.
- Added nodejs/utils/build_info.js (buildVersion/buildHash/buildYear,
  read once from package.json + git) and wired it into routes/render.js
  so every page has the values the footer needs. Mirrors the same
  helper added to sso-manager-node in the matching cleanup there.
- Copied the theta42.svg logo into nodejs/public/img/ (previously only
  present in sso-manager-node) so both apps' footers render identically.

Verified by rendering top+bottom with the real ejs package: no
template errors, GitHub link present exactly once (in the footer, not
the nav), logo and MIT License link present. npm test: 192/192 pass
(unaffected — view-only + a new leaf utility module).

nodejs/views/top.ejs

@@ -76,11 +76,6 @@
 							API Tokens
 						</a>
 					</li>
-					<li class="nav-item">
-						<a class="nav-link" href="https://github.com/theta42/proxy" target="_blank">
-							<i class="fa-brands fa-github"></i>
-						</a>
-					</li>
 				</ul>
 				<div class="form-inline mt-2 mt-md-0">
 					<a id="cl-username" class="navbar-text text-light me-3" href="/profile" style="display: none;">