refactor: deduplicate modals, notifications, confirms, comboboxes, proficiency

Modal Overlay (Finding 1 — 6 admin files):
- Migrated CountriesClient, ManagementLevelsClient, OrgUnitsClient,
  CalculationRulesClient, UtilizationCategoriesClient, RoleModal
  from inline fixed-overlay to AnimatedModal component
- Gains: animated transitions, backdrop blur, escape key for free

Notification Helper (Finding 9 — 9 API files, 14 call sites):
- New createNotification() + createNotificationsForUsers() in
  packages/api/src/lib/create-notification.ts
- Handles exactOptionalPropertyTypes spread + SSE emit internally
- Simplified: budget-alerts, estimate-reminders, auto-staffing,
  vacation-conflicts, chargeability-alerts, comment, vacation, notification

ConfirmDialog (Finding 3 — 11 files):
- Replaced all window.confirm() calls with ConfirmDialog component
- Files: CommentThread, EffortRules, ExperienceMultipliers,
  ManagementLevels, CalculationRules, Countries, RateCards,
  ApplyEffortRules, ApplyExperienceMultipliers, NotificationCenter,
  ReminderModal

EntityCombobox (Finding 4 — 3 files):
- New generic EntityCombobox<T> with customization hooks
- ResourceCombobox + ProjectCombobox rewritten as thin wrappers
- All consumers unchanged (backwards-compatible props)

Proficiency Constants (Finding 2 — 2 files):
- SkillsAnalytics + SkillMarketplace now import from skills/shared.tsx
- Deleted ~70 LOC of local duplicate definitions

Regression: 283 engine + 37 staffing tests pass. TypeScript clean.
AI Assistant: all 87 tools verified accessible.

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

apps/web/src/components/notifications/NotificationCenterClient.tsx

@@ -2,6 +2,7 @@
 
 import { useState } from "react";
 import { useSearchParams } from "next/navigation";
+import { ConfirmDialog } from "~/components/ui/ConfirmDialog.js";
 import { trpc } from "~/lib/trpc/client.js";
 import { usePermissions } from "~/hooks/usePermissions.js";
 import { TaskCard } from "./TaskCard.js";
@@ -31,6 +32,7 @@ export function NotificationCenterClient() {
   const [activeTab, setActiveTab] = useState<TabKey>(initialTab);
   const { canEdit } = usePermissions();
   const [showTaskModal, setShowTaskModal] = useState(false);
+  const [confirmDeleteReminder, setConfirmDeleteReminder] = useState<string | null>(null);
   const [reminderModal, setReminderModal] = useState<{
     open: boolean;
     reminder: {
@@ -374,11 +376,7 @@ export function NotificationCenterClient() {
                         </button>
                         <button
                           type="button"
-                          onClick={() => {
-                            if (window.confirm("Delete this reminder?")) {
-                              deleteReminder.mutate({ id: r.id });
-                            }
-                          }}
+                          onClick={() => setConfirmDeleteReminder(r.id)}
                           disabled={deleteReminder.isPending}
                           className="p-1 text-gray-400 hover:text-red-600 dark:hover:text-red-400 hover:bg-gray-100 dark:hover:bg-gray-800 rounded transition-colors"
                           title="Delete"
@@ -413,6 +411,20 @@ export function NotificationCenterClient() {
           onSuccess={() => setShowTaskModal(false)}
         />
       )}
+
+      {confirmDeleteReminder && (
+        <ConfirmDialog
+          title="Delete reminder"
+          message="Are you sure you want to delete this reminder?"
+          confirmLabel="Delete"
+          variant="danger"
+          onConfirm={() => {
+            deleteReminder.mutate({ id: confirmDeleteReminder });
+            setConfirmDeleteReminder(null);
+          }}
+          onCancel={() => setConfirmDeleteReminder(null)}
+        />
+      )}
     </div>
   );
 }