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/admin/ExperienceMultipliersClient.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import { useState } from "react";
+import { ConfirmDialog } from "~/components/ui/ConfirmDialog.js";
 import { InfoTooltip } from "~/components/ui/InfoTooltip.js";
 import { trpc } from "~/lib/trpc/client.js";
 
@@ -97,6 +98,7 @@ export function ExperienceMultipliersClient() {
 
   const [editing, setEditing] = useState<EditingSet | null>(null);
   const [expandedId, setExpandedId] = useState<string | null>(null);
+  const [confirmDelete, setConfirmDelete] = useState<string | null>(null);
 
   function handleSave() {
     if (!editing) return;
@@ -422,11 +424,7 @@ export function ExperienceMultipliersClient() {
                 Edit
               </button>
               <button
-                onClick={() => {
-                  if (confirm(`Delete multiplier set "${s.name}"?`)) {
-                    deleteMutation.mutate({ id: s.id });
-                  }
-                }}
+                onClick={() => setConfirmDelete(s.id)}
                 className="rounded-xl border border-red-200 px-3 py-1 text-xs font-medium text-red-600 hover:bg-red-50"
               >
                 Delete
@@ -471,6 +469,20 @@ export function ExperienceMultipliersClient() {
           )}
         </div>
       ))}
+
+      {confirmDelete && (
+        <ConfirmDialog
+          title="Delete multiplier set"
+          message="Are you sure you want to delete this multiplier set? This action cannot be undone."
+          confirmLabel="Delete"
+          variant="danger"
+          onConfirm={() => {
+            deleteMutation.mutate({ id: confirmDelete });
+            setConfirmDelete(null);
+          }}
+          onCancel={() => setConfirmDelete(null)}
+        />
+      )}
     </div>
   );
 }