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/budget-alerts.ts

@@ -1,5 +1,5 @@
 import { listAssignmentBookings } from "@planarchy/application";
-import { emitNotificationCreated } from "../sse/event-bus.js";
+import { createNotificationsForUsers } from "./create-notification.js";
 
 type DbClient = Parameters<typeof listAssignmentBookings>[0] & {
   project: {
@@ -119,23 +119,18 @@ export async function checkBudgetThresholds(
       { minimumFractionDigits: 2, maximumFractionDigits: 2 },
     );
 
-    for (const manager of managers) {
-      const notification = await db.notification.create({
-        data: {
-          userId: manager.id,
-          type: threshold.type,
-          category: "NOTIFICATION",
-          priority: threshold.priority,
-          title: `Budget alert: ${project.name} has reached ${threshold.label} of budget`,
-          body: `Project ${project.shortCode} "${project.name}" has spent ${formattedSpend} EUR of ${formattedBudget} EUR budget (${Math.round(spendPercent)}%).`,
-          entityId: projectId,
-          entityType: "project_budget",
-          link: `/projects/${projectId}`,
-          channel: "in_app",
-        },
-      });
-
-      emitNotificationCreated(manager.id, notification.id);
-    }
+    await createNotificationsForUsers({
+      db,
+      userIds: managers.map((m) => m.id),
+      type: threshold.type,
+      category: "NOTIFICATION",
+      priority: threshold.priority,
+      title: `Budget alert: ${project.name} has reached ${threshold.label} of budget`,
+      body: `Project ${project.shortCode} "${project.name}" has spent ${formattedSpend} EUR of ${formattedBudget} EUR budget (${Math.round(spendPercent)}%).`,
+      entityId: projectId,
+      entityType: "project_budget",
+      link: `/projects/${projectId}`,
+      channel: "in_app",
+    });
   }
 }