fix: serve logo locally to fix broken image on nav/footer

External URL was unreachable from tools subdomain (CSP or cross-origin block),
causing a grey placeholder rectangle. Logo now served from assets/images/ and
brightness/invert filter removed — logo is white-on-transparent, displays
correctly on dark nav and footer without filtering.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/css/tools.css

@@ -4469,8 +4469,6 @@ body.lt-landing {
 .lt-nav__logo {
   height: 34px;
   width: auto;
-  filter: brightness(0) invert(1);
-  opacity: 0.90;
   display: block;
 }
 
@@ -4943,8 +4941,7 @@ body.lt-landing {
 .lt-footer__logo {
   height: 32px;
   width: auto;
-  filter: brightness(0) invert(1);
-  opacity: 0.78;
+  opacity: 0.85;
   display: block;
   margin-bottom: 1.1rem;
 }