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>

packages/api/src/lib/vacation-conflicts.ts

@@ -1,5 +1,5 @@
 import { VacationStatus } from "@planarchy/db";
-import { emitNotificationCreated } from "../sse/event-bus.js";
+import { createNotification } from "./create-notification.js";
 
 type DbClient = {
   vacation: {
@@ -189,21 +189,19 @@ export async function checkVacationConflicts(
 
     // Create a notification for the approver if provided
     if (approverUserId) {
-      const notification = await db.notification.create({
-        data: {
-          userId: approverUserId,
-          type: "VACATION_CONFLICT_WARNING",
-          category: "NOTIFICATION",
-          priority: "HIGH",
-          title: `Vacation conflict warning: ${vacation.resource.displayName}`,
-          body: warning,
-          entityId: vacationId,
-          entityType: "vacation",
-          link: "/vacations",
-          channel: "in_app",
-        },
+      await createNotification({
+        db,
+        userId: approverUserId,
+        type: "VACATION_CONFLICT_WARNING",
+        category: "NOTIFICATION",
+        priority: "HIGH",
+        title: `Vacation conflict warning: ${vacation.resource.displayName}`,
+        body: warning,
+        entityId: vacationId,
+        entityType: "vacation",
+        link: "/vacations",
+        channel: "in_app",
       });
-      emitNotificationCreated(approverUserId, notification.id);
     }
   }