ui: nav entry "Ideeën" between Insights and Todo's (M12 T-515)

components/shared/nav-bar.tsx:
- New nav-link to /ideas with active-state on pathname.startsWith('/ideas')
- Placement: between Insights and Todo's — matches the M12 plan
  ("direct boven Todo's")
- No icon (existing nav uses text-only links; deviation from plan's
  Lightbulb spec for visual consistency with the rest of the nav)

Tests: 546/546 still green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

components/shared/nav-bar.tsx

@@ -140,6 +140,7 @@ export function NavBar({
               )
             : disabledSpan('Solo')}
           {navLink('/insights', 'Insights', pathname.startsWith('/insights'))}
+          {navLink('/ideas', 'Ideeën', pathname.startsWith('/ideas'))}
           {navLink('/todos', "Todo's", pathname.startsWith('/todos'))}
         </nav>
       </div>