refactor: remove obsolete scaffolding and dead modules

Drop the unused root hello-world controller, empty CommonModule imports, development seeding code, legacy student report entity, stale DTOs, notification hook, and their placeholder tests.

apps/admin/src/hooks/useNotifications.ts

@@ -1,78 +0,0 @@
-import { useState, useEffect, useCallback } from 'react';
-import api from '../api';
-
-interface Notification {
-  id: number;
-  type: string;
-  title: string;
-  content: string;
-  link: string | null;
-  createdAt: string;
-}
-
-export function useNotifications() {
-  const [unreadCount, setUnreadCount] = useState(0);
-  const [latestNotification, setLatestNotification] = useState<Notification | null>(null);
-
-  const fetchUnreadCount = useCallback(async () => {
-    try {
-      const data = await api.get('/notifications/unread-count') as unknown as { count: number };
-      setUnreadCount(data.count);
-    } catch {
-      // silent
-    }
-  }, []);
-
-  useEffect(() => {
-    fetchUnreadCount();
-
-    const token = localStorage.getItem('token');
-    if (!token) return;
-
-    const es = new EventSource(`/api/notifications/stream?token=${encodeURIComponent(token)}`);
-
-    es.onmessage = (event) => {
-      try {
-        const notification = JSON.parse(event.data) as Notification;
-        setUnreadCount((c) => c + 1);
-        setLatestNotification(notification);
-      } catch {
-        // ignore parse errors
-      }
-    };
-
-    const pollRef = { current: undefined as number | undefined };
-
-    es.onerror = () => {
-      es.close();
-      pollRef.current = setInterval(() => {
-        fetchUnreadCount();
-      }, 60_000);
-    };
-
-    return () => {
-      es.close();
-      if (pollRef.current !== undefined) clearInterval(pollRef.current);
-    };
-  }, [fetchUnreadCount]);
-
-  const markAsRead = useCallback(async (id: number) => {
-    try {
-      await api.put(`/notifications/${id}/read`);
-      setUnreadCount((c) => Math.max(0, c - 1));
-    } catch {
-      // silent
-    }
-  }, []);
-
-  const markAllAsRead = useCallback(async () => {
-    try {
-      await api.put('/notifications/read-all');
-      setUnreadCount(0);
-    } catch {
-      // silent
-    }
-  }, []);
-
-  return { unreadCount, latestNotification, markAsRead, markAllAsRead };
-}