feat(ui): improve settings modal with tabs and bolder Run Claude text

- Add tabbed interface to App Settings modal (Display, Claude CLI, Paths)
- Add modal-lg class for wider settings modal (520px)
- Remove "(will be created)" text from empty case display
- Make Run Claude button text bolder (font-weight: 700)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/web/public/styles.css

@@ -1163,7 +1163,7 @@ body {
   background: linear-gradient(135deg, #1e3a5f 0%, #3d2a5c 100%);
   border-color: #2d4a6f;
   color: var(--accent-hover);
-  font-weight: 500;
+  font-weight: 700;
   padding: 0.4rem 0.85rem;
 }
 
@@ -1728,6 +1728,10 @@ body {
   max-width: 340px;
 }
 
+.modal-content.modal-lg {
+  max-width: 520px;
+}
+
 .modal-warning-text {
   color: var(--text-dim);
   font-size: 0.85rem;