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/estimates/ApplyExperienceMultipliers.tsx

@@ -2,6 +2,7 @@
 
 import { useState } from "react";
 import { clsx } from "clsx";
+import { ConfirmDialog } from "~/components/ui/ConfirmDialog.js";
 import { InfoTooltip } from "~/components/ui/InfoTooltip.js";
 import { formatCents } from "~/lib/format.js";
 import { trpc } from "~/lib/trpc/client.js";
@@ -18,6 +19,7 @@ export function ApplyExperienceMultipliers({ estimateId, canEdit, onApplied }: A
 
   const [selectedSetId, setSelectedSetId] = useState<string>("");
   const [showPreview, setShowPreview] = useState(false);
+  const [confirmApply, setConfirmApply] = useState(false);
 
   const previewQuery = trpc.experienceMultiplier.preview.useQuery(
     { estimateId, multiplierSetId: selectedSetId },
@@ -96,9 +98,7 @@ export function ApplyExperienceMultipliers({ estimateId, canEdit, onApplied }: A
         <button
           onClick={() => {
             if (!selectedSetId) return;
-            if (confirm("This will update cost/bill rates and hours on matching demand lines. Continue?")) {
-              applyMutation.mutate({ estimateId, multiplierSetId: selectedSetId });
-            }
+            setConfirmApply(true);
           }}
           disabled={!selectedSetId || applyMutation.isPending}
           className="rounded-2xl bg-brand-600 px-4 py-2 text-sm font-medium text-white hover:bg-brand-700 disabled:opacity-50"
@@ -204,6 +204,19 @@ export function ApplyExperienceMultipliers({ estimateId, canEdit, onApplied }: A
       {showPreview && previewQuery.isLoading && (
         <p className="mt-3 text-sm text-gray-400">Computing preview...</p>
       )}
+
+      {confirmApply && (
+        <ConfirmDialog
+          title="Apply experience multipliers"
+          message="This will update cost/bill rates and hours on matching demand lines. Continue?"
+          confirmLabel="Apply"
+          onConfirm={() => {
+            applyMutation.mutate({ estimateId, multiplierSetId: selectedSetId });
+            setConfirmApply(false);
+          }}
+          onCancel={() => setConfirmApply(false)}
+        />
+      )}
     </div>
   );
 }