refactor: replace dynamic imports with event bus pattern

Replace 12 dynamic `await import()` calls with domain events emitted
through the existing systemEvents bus, breaking circular dependencies
between services (economy/inventory/leveling -> quest, * -> dashboard).

- Add `emitAsync` to SystemEventEmitter for sequential listener awaiting,
  preserving DB transaction atomicity for quest progress tracking
- Add DOMAIN event constants (BALANCE_CHANGED, XP_GAINED, ITEM_COLLECTED,
  ITEM_USED, TRANSFER_COMPLETED, DAILY_CLAIMED, TRIVIA_*, EXAM_PASSED)
- Create shared/lib/eventWiring.ts to register all domain event listeners
- Convert quest event calls to `await systemEvents.emitAsync()` (5 calls)
- Convert dashboard event calls to `systemEvents.emit()` fire-and-forget (5 calls)
- Convert exam.service.ts userService import to static import (1 call)
- Convert dashboard.service.ts events import to static import (1 call)
- Leave inventory.service.ts validateAndExecuteEffect import unchanged (Task 3)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/modules/economy/exam.service.ts

@@ -2,6 +2,8 @@ import { users, userTimers, transactions } from "@db/schema";
 import { eq, and, sql } from "drizzle-orm";
 import { TimerType, TransactionType } from "@shared/lib/constants";
 import { config } from "@shared/lib/config";
+import { systemEvents, EVENTS } from "@shared/lib/events";
+import { userService } from "@shared/modules/user/user.service";
 import { withTransaction } from "@/lib/db";
 import type { Transaction } from "@shared/lib/types";
 import { UserError, SystemError } from "@shared/lib/errors";
@@ -84,7 +86,6 @@ export const examService = {
     async registerForExam(userId: string, username: string, tx?: Transaction): Promise<ExamActionResult> {
         return await withTransaction(async (txFn) => {
             // Ensure user exists
-            const { userService } = await import("@shared/modules/user/user.service");
             const user = await userService.getOrCreateUser(userId, username, txFn);
             if (!user) throw new SystemError("Failed to get or create user.");
 
@@ -242,12 +243,7 @@ export const examService = {
             }
 
             // Record dashboard event
-            const { dashboardService } = await import("@shared/modules/dashboard/dashboard.service");
-            await dashboardService.recordEvent({
-                type: 'success',
-                message: `${user.username} passed their exam: ${reward.toLocaleString()} AU`,
-                icon: '🎓'
-            });
+            systemEvents.emit(EVENTS.DOMAIN.EXAM_PASSED, { username: user.username, reward });
 
             return {
                 status: ExamStatus.AVAILABLE,