style: Double logo size to 5rem, increase brand title font by 30% to 1.95rem

client/src/App.css

@@ -27,7 +27,7 @@
   gap: 0.75rem;
   color: var(--text-primary);
   font-weight: 700;
-  font-size: 1.5rem;
+  font-size: 1.95rem; /* +30% from 1.5rem */
   text-decoration: none;
   transition: var(--transition);
 }
@@ -36,10 +36,10 @@
   color: var(--primary-light);
 }
 
-/* Square logo: fixed equal width/height to match a 1:1 image */
+/* Square logo: doubled from 2.5rem to 5rem */
 .brand-logo {
-  width: 2.5rem;
-  height: 2.5rem;
+  width: 5rem;
+  height: 5rem;
   object-fit: contain;
   object-position: center;
   display: block;
@@ -51,8 +51,8 @@
   display: flex;
   align-items: center;
   justify-content: center;
-  width: 2.5rem;
-  height: 2.5rem;
+  width: 5rem;
+  height: 5rem;
   background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
   border-radius: var(--radius);
   box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
@@ -108,18 +108,18 @@
   }
   
   .nav-brand {
-    font-size: 1.25rem;
+    font-size: 1.625rem; /* +30% from 1.25rem */
   }
   
-  /* Scale square logo down on mobile */
+  /* Scale square logo down on mobile (doubled from 2rem) */
   .brand-logo {
-    width: 2rem;
-    height: 2rem;
+    width: 4rem;
+    height: 4rem;
   }
 
   .brand-icon {
-    width: 2rem;
-    height: 2rem;
+    width: 4rem;
+    height: 4rem;
   }
   
   .nav-links {