fix(practice): always show add student FAB button

The FAB button should always be available for creating students
without auto-enrollment. Teachers now have both:
- FAB button: creates student only
- Classroom card button: creates student and auto-enrolls

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/components/practice/StudentFilterBar.tsx

@@ -528,8 +528,8 @@ export function StudentFilterBar({
           </>
         )}
 
-        {/* Add Student FAB - only for parents (teachers have button in classroom card) */}
-        {onAddStudent && !classroom && (
+        {/* Add Student FAB - always available for creating students */}
+        {onAddStudent && (
           <button
             type="button"
             onClick={onAddStudent}