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/assets/theme.css

@@ -1,3 +1,5 @@
+@import url('https://fonts.googleapis.com/css2?family=Fraunces:ital,opsz,wght@0,9..144,300..900;1,9..144,300..900&display=swap');
+
 :root {
   --color-bg: #f5f5fb;
   --color-bg-secondary: #ededf5;
@@ -111,6 +113,11 @@ body {
   transition: background-color 0.2s, color 0.2s;
 }
 
+h1, h2, h3 {
+  font-family: 'Fraunces', Georgia, serif;
+  font-optical-sizing: auto;
+}
+
 input:focus-visible,
 textarea:focus-visible,
 select:focus-visible,