fix: reset join request toast state when moderation event cleared

**Issue:**
Toast notification was persisting after successful approval because
showJoinRequestToast state was never reset to false.

**Fix:**
- Add else clause to useEffect that resets toast state when event cleared
- Reset both showJoinRequestToast and requestError when event changes type
- Ensures toast properly dismisses after approval/denial

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

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

apps/web/src/components/nav/ModerationNotifications.tsx

@@ -52,6 +52,10 @@ export function ModerationNotifications({
     if (moderationEvent?.type === 'join-request') {
       setShowJoinRequestToast(true)
       setRequestError(null) // Clear any previous errors
+    } else {
+      // Reset toast state when event is cleared or changes type
+      setShowJoinRequestToast(false)
+      setRequestError(null)
     }
   }, [moderationEvent])