style: Add subtle diffuse black drop shadow to logo and brand title text

client/src/App.css

@@ -45,6 +45,9 @@
   display: block;
   border-radius: 4px;
   flex-shrink: 0;
+  /* Subtle diffuse black drop shadow for depth */
+  filter: drop-shadow(0 2px 6px rgba(0, 0, 0, 0.45))
+          drop-shadow(0 1px 2px rgba(0, 0, 0, 0.30));
 }
 
 .brand-icon {
@@ -65,6 +68,9 @@
   -webkit-background-clip: text;
   -webkit-text-fill-color: transparent;
   background-clip: text;
+  /* text-shadow doesn't work with background-clip:text — use filter instead */
+  filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.50))
+          drop-shadow(0 1px 2px rgba(0, 0, 0, 0.30));
 }
 
 .nav-links {