feat(fe): Add form field navigation - Enter key moves to next field

- Create useFormFieldNavigation composable for Tab-like Enter behavior
- KsTextField: Enter -> next field
- KsTextArea: Ctrl+Enter for newline, Enter -> next field
- KsSelect: Enter -> next field after selection
- Implements standard form navigation pattern across input components

frontend/src/shared/shell/KsAppShell.vue

@@ -76,14 +76,12 @@ onMounted(() => {
       </main>
     </div>
 
-    <!-- Footer -->
-    <KsFooter />
-
     <!-- Notifications (toasts) -->
     <KsNotifications />
   </div>
 </template>
 
+
 <style scoped>
 .ks-app-shell {
   display: flex;