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/create-notification.ts

@@ -0,0 +1,102 @@
+import { emitNotificationCreated } from "../sse/event-bus.js";
+
+export interface CreateNotificationParams {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  db: { notification: { create: (args: any) => Promise<{ id: string; userId: string }> } };
+  userId: string;
+  type: string;
+  title: string;
+  body?: string | undefined;
+  link?: string | undefined;
+  entityId?: string | undefined;
+  entityType?: string | undefined;
+  category?: string | undefined;
+  priority?: string | undefined;
+  senderId?: string | undefined;
+  channel?: string | undefined;
+  taskStatus?: string | undefined;
+  taskAction?: string | undefined;
+  assigneeId?: string | undefined;
+  dueDate?: Date | undefined;
+  sourceId?: string | undefined;
+  /** Set to false to suppress the SSE emitNotificationCreated call. Default: true. */
+  emit?: boolean | undefined;
+}
+
+/**
+ * Create a single in-app notification and optionally emit an SSE event.
+ *
+ * Handles the `exactOptionalPropertyTypes` spread pattern internally so
+ * callers do not need to repeat the `...(val !== undefined ? { key: val } : {})` boilerplate.
+ *
+ * Returns the created notification's ID.
+ */
+export async function createNotification(
+  params: CreateNotificationParams,
+): Promise<string> {
+  const {
+    db,
+    userId,
+    type,
+    title,
+    body,
+    link,
+    entityId,
+    entityType,
+    category,
+    priority,
+    senderId,
+    channel,
+    taskStatus,
+    taskAction,
+    assigneeId,
+    dueDate,
+    sourceId,
+    emit = true,
+  } = params;
+
+  const notification = await db.notification.create({
+    data: {
+      userId,
+      type,
+      title,
+      ...(body !== undefined ? { body } : {}),
+      ...(link !== undefined ? { link } : {}),
+      ...(entityId !== undefined ? { entityId } : {}),
+      ...(entityType !== undefined ? { entityType } : {}),
+      ...(category !== undefined ? { category } : {}),
+      ...(priority !== undefined ? { priority } : {}),
+      ...(senderId !== undefined ? { senderId } : {}),
+      ...(channel !== undefined ? { channel } : {}),
+      ...(taskStatus !== undefined ? { taskStatus } : {}),
+      ...(taskAction !== undefined ? { taskAction } : {}),
+      ...(assigneeId !== undefined ? { assigneeId } : {}),
+      ...(dueDate !== undefined ? { dueDate } : {}),
+      ...(sourceId !== undefined ? { sourceId } : {}),
+    },
+  });
+
+  if (emit) {
+    emitNotificationCreated(userId, notification.id);
+  }
+
+  return notification.id;
+}
+
+/**
+ * Create one notification per user ID.
+ *
+ * Useful for fan-out scenarios (e.g. notifying all managers).
+ * Returns the count of notifications created.
+ */
+export async function createNotificationsForUsers(
+  params: Omit<CreateNotificationParams, "userId"> & { userIds: string[] },
+): Promise<number> {
+  const { userIds, ...rest } = params;
+  let count = 0;
+  for (const userId of userIds) {
+    await createNotification({ ...rest, userId });
+    count++;
+  }
+  return count;
+}