feat: enterprise notification & task management system

Phase N.1 — Data Model:
- Extend Notification model with category, priority, task fields (status, action,
  assignee, dueDate, completedAt/By), reminder fields (remindAt, recurrence,
  nextRemindAt), and targeting metadata (sourceId, senderId, channel)
- Add NotificationCategory, NotificationPriority, TaskStatus enums
- Add NotificationBroadcast model for group notifications
- Shared types with parseTaskAction()/buildTaskAction() helpers

Phase N.2 — API:
- Extend notification router: listTasks, taskCounts, updateTaskStatus,
  createReminder/update/delete/list, createBroadcast/listBroadcasts,
  createTask, assignTask, delete
- Broadcast targeting: resolve recipients by user/role/project/orgUnit/all
- Task-action registry: approve_vacation, reject_vacation, confirm_assignment
- Reminder scheduler: 60s poll interval, recurring support, catch-up on start
- SSE events: TASK_ASSIGNED, TASK_COMPLETED, TASK_STATUS_CHANGED,
  REMINDER_DUE, BROADCAST_SENT

Phase N.3 — AI Assistant:
- 7 new tools: list_tasks, get_task_detail, update_task_status,
  execute_task_action, create_reminder, create_task_for_user, send_broadcast
- execute_task_action dispatches to task-action registry with per-action
  permission checks, marks tasks as completed by AI

Phase N.4 — Frontend:
- Enhanced NotificationBell with task badge, tabs (All/Tasks/Reminders)
- TaskCard component with priority badges, due dates, action buttons
- ReminderModal for creating/editing personal reminders
- BroadcastModal for targeted group notifications (manager+)
- NotificationCenter full-page with 5 tabs and bulk actions
- TaskWidget dashboard widget showing open tasks
- Admin broadcast management page
- AppShell nav links for Notifications and Broadcasts
- SSE hook handlers for task/reminder events

Phase N.5 — Auto-Tasks:
- Vacation create → APPROVAL tasks for all managers
- Vacation approve/reject → mark approval tasks as DONE
- Demand create → TASK for managers to fill staffing needs

Co-Authored-By: claude-flow <ruv@ruv.net>

packages/api/src/router/assistant.ts

@@ -23,6 +23,9 @@ Deine Fähigkeiten:
 - Rollen, Clients, Org-Units erstellen/aktualisieren/löschen
 - Estimates erstellen, Rate Cards abrufen, Blueprints anzeigen
 - Notifications anzeigen, Dashboard-Details abrufen
+- Tasks einsehen, Status ändern, Tasks erledigen (approve vacation, confirm allocation, etc.)
+- Persönliche Erinnerungen anlegen (einmalig oder wiederkehrend)
+- Tasks für andere User erstellen, Broadcasts an Gruppen senden
 - Den User zu relevanten Seiten navigieren (Timeline, Dashboard, etc. mit Filtern)
 - Verfügbarkeit von Ressourcen prüfen, Kapazitäten suchen
 
@@ -75,6 +78,10 @@ const TOOL_PERMISSION_MAP: Record<string, string> = {
   reject_vacation: "manageVacations",
   cancel_vacation: "manageVacations",
   set_entitlement: "manageVacations",
+  // Task management
+  create_task_for_user: "manageProjects",
+  send_broadcast: "manageProjects",
+  execute_task_action: "manageAllocations",
 };
 
 /** Tools that require cost visibility */
@@ -153,7 +160,7 @@ export const assistantRouter = createTRPCRouter({
       });
 
       // 5. Function calling loop
-      const toolCtx: ToolContext = { db: ctx.db, userRole, permissions };
+      const toolCtx: ToolContext = { db: ctx.db, userId: ctx.dbUser!.id, userRole, permissions };
       const collectedActions: ToolAction[] = [];
 
       for (let i = 0; i < MAX_TOOL_ITERATIONS; i++) {