Add WB logo image to all pages

Replace text "WB" placeholder with wb.png in topbar and login/register pages.

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

static/styles.css

@@ -128,6 +128,13 @@ a:hover { color: var(--blue-dark); text-decoration: underline; }
     box-shadow: 0 4px 14px var(--wb-glow);
     flex-shrink: 0;
 }
+.topbar__logo-img {
+    width: 34px;
+    height: 34px;
+    border-radius: var(--r-sm);
+    object-fit: contain;
+    flex-shrink: 0;
+}
 
 .topbar__name {
     font-size: 15px;
@@ -912,6 +919,11 @@ textarea:focus {
     font-weight: 800;
     box-shadow: 0 4px 14px var(--wb-glow);
 }
+.auth-kicker-logo-img {
+    width: 48px;
+    height: 48px;
+    object-fit: contain;
+}
 
 .auth-kicker-text {
     font-size: 14px;