fix(webserver): correct default template layout glitches after HTML5 switch - #204

…switch

The HTML5 doctype upgrade (standards mode) introduced inline-image
descender gaps that were fixed for some images but missed two, and
exposed a pre-existing layout inconsistency on the shared page:

- Login page: give the logo image display:block so its descender gap no
  longer makes the banner row taller than its background, which left a
  thin white line below the login box. Add a login-logo class to scope
  the rule.
- Navbar: give the col.png separator (the only inline <img> in the
  navbar) display:block, removing the ~2px descender gap that made the
  bar taller and pushed all page content down by 2px.
- Shared page: add the 10px spacer between the action toolbar and the
  content box that the downloads page already has, so both toolbar
  pages share the same header-to-content separation.
- Login page: make the "Enter password" label black instead of the
  inherited dark blue.