UI polish: Illuminated Transcript design language

- Fraunces serif for headings and assistant identity label
- Chat bubbles flipped: assistant responses elevated (card + left indigo
  accent + shadow), user prompts ghosted (transparent bg, muted text)
- AppLogo: book fill changed from text-color to indigo in light mode
- AppHeader: border-bottom removed; active nav uses underline accent
- NoteCard/TaskCard: border replaced with whisper indigo-tint shadow
- HomeView: dashboard-response uses left accent; progress bars indigo;
  empty-state decorative marker; project cards use shadow depth
- NotesListView: btn-new/btn-cta use indigo gradient + glow
- All primary CTA buttons: indigo gradient (135deg #6366f1 → #4f46e5)
  with box-shadow glow on hover
- Dark palette: navy (#1a1a2e family) → slate-indigo (#111113 family)
- Scrollbars: thin 4px indigo-tinted

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

frontend/src/views/NotesListView.vue

@@ -201,11 +201,16 @@ function onOffsetUpdate(offset: number) {
 }
 .btn-new {
   padding: 0.45rem 1rem;
-  background: var(--color-primary);
+  background: linear-gradient(135deg, #6366f1, #4f46e5);
   color: #fff;
   border-radius: var(--radius-sm);
   text-decoration: none;
   font-size: 0.9rem;
+  box-shadow: 0 1px 6px rgba(99, 102, 241, 0.25);
+}
+.btn-new:hover {
+  box-shadow: 0 3px 12px rgba(99, 102, 241, 0.45);
+  filter: brightness(1.08);
 }
 .controls {
   display: flex;
@@ -312,11 +317,16 @@ function onOffsetUpdate(offset: number) {
 .btn-cta {
   display: inline-block;
   padding: 0.45rem 1rem;
-  background: var(--color-primary);
+  background: linear-gradient(135deg, #6366f1, #4f46e5);
   color: #fff;
   border-radius: var(--radius-sm);
   text-decoration: none;
   font-size: 0.9rem;
+  box-shadow: 0 1px 6px rgba(99, 102, 241, 0.25);
+}
+.btn-cta:hover {
+  box-shadow: 0 3px 12px rgba(99, 102, 241, 0.45);
+  filter: brightness(1.08);
 }
 
 .kb-active-item {