feat(dashboard): replace current book placeholder with real user data

- Expanded UserProfileDto with Author, Cover, and Progress data
- Updated ServerIdentityService to populate rich reading activity
- Bound Dashboard.razor to real IdentityService data
- Implemented premium empty state for new users
- Refined dashboard typography and CSS depth

src/NexusReader.UI.Shared/Pages/Dashboard.razor.css

@@ -79,6 +79,19 @@
     font-weight: 500;
     color: #ffffff;
     letter-spacing: 1px;
+    text-transform: lowercase;
+}
+
+.username::before {
+    content: '[';
+    color: var(--nexus-neon);
+    margin-right: 4px;
+}
+
+.username::after {
+    content: ']';
+    color: var(--nexus-neon);
+    margin-left: 4px;
 }
 
 .status-pills {
@@ -359,6 +372,27 @@
     filter: brightness(1.1);
 }
 
+/* Empty State */
+.empty-state {
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    padding: 3rem 1rem;
+    text-align: center;
+    gap: 1.5rem !important;
+}
+
+.empty-icon {
+    opacity: 0.3;
+    color: var(--nexus-neon);
+    filter: drop-shadow(0 0 10px rgba(0, 255, 153, 0.2));
+}
+
+.empty-state .reading-info {
+    align-items: center;
+    max-width: 400px;
+}
+
 @media (max-width: 1024px) {
     .main-grid {
         grid-template-columns: 1fr;