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/auto-staffing.ts

@@ -1,7 +1,7 @@
 import { listAssignmentBookings } from "@planarchy/application";
 import { rankResources } from "@planarchy/staffing";
 import type { SkillEntry } from "@planarchy/shared";
-import { emitNotificationCreated } from "../sse/event-bus.js";
+import { createNotificationsForUsers } from "./create-notification.js";
 
 /**
  * Minimal DB interface for auto-staffing — avoids importing the full PrismaClient.
@@ -227,24 +227,19 @@ export async function generateAutoSuggestions(
       select: { id: true },
     });
 
-    for (const manager of managers) {
-      const notification = await db.notification.create({
-        data: {
-          userId: manager.id,
-          type: "AUTO_STAFFING_SUGGESTION",
-          category: "NOTIFICATION",
-          priority: "NORMAL",
-          title,
-          body,
-          entityId: demandRequirementId,
-          entityType: "demand",
-          link: `/staffing?demandId=${demandRequirementId}`,
-          channel: "in_app",
-        },
-      });
-
-      emitNotificationCreated(manager.id, notification.id);
-    }
+    await createNotificationsForUsers({
+      db,
+      userIds: managers.map((m) => m.id),
+      type: "AUTO_STAFFING_SUGGESTION",
+      category: "NOTIFICATION",
+      priority: "NORMAL",
+      title,
+      body,
+      entityId: demandRequirementId,
+      entityType: "demand",
+      link: `/staffing?demandId=${demandRequirementId}`,
+      channel: "in_app",
+    });
   } catch {
     // Fire-and-forget: swallow all errors to avoid disrupting the caller.
   }