fix(F2,F3): onboarding chip in Header, auth catch-all redirects to dashboard

F3: authenticated unknown routes now redirect to /dashboard instead of
rendering private NotFound.

F2: Header shows a warning Chip with the current onboarding next_step
when the user has not completed onboarding (next_step != 'ready').
Chip navigates to /dashboard on click. Hidden on xs screens.

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

src/AppRoutes.tsx

@@ -169,8 +169,8 @@ const AppRoutes: React.FC = () => {
           </Route>
         )}
 
-        {/* Fallback route - use different NotFound pages based on auth state */}
-        <Route path="*" element={user ? <NotFound /> : <NotFoundPublic />} />
+        {/* Fallback route - authenticated users go to dashboard, unauthenticated see public 404 */}
+        <Route path="*" element={user ? <Navigate to="/dashboard" replace /> : <NotFoundPublic />} />
       </Routes>
     </Layout>
   );

src/pages/Header.tsx

@@ -7,6 +7,7 @@ import {
   Typography,
   IconButton,
   Box,
+  Chip,
   useTheme,
   Menu,
   MenuItem,
@@ -126,6 +127,15 @@ const Header: React.FC = () => {
         </Typography>
 
         <Box sx={{ display: 'flex', alignItems: 'center', gap: 2 }}>
+          {isAuthenticated && bootstrapData?.onboarding?.next_step && bootstrapData.onboarding.next_step !== 'ready' && (
+            <Chip
+              label={bootstrapData.onboarding.next_step.replace(/_/g, ' ')}
+              color="warning"
+              size="small"
+              onClick={() => navigate('/dashboard')}
+              sx={{ cursor: 'pointer', display: { xs: 'none', sm: 'flex' } }}
+            />
+          )}
           {isAuthenticated && (
             <Typography
               variant="body2"