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/leveling/leveling.service.ts

@@ -2,6 +2,7 @@ import { users, userTimers } from "@db/schema";
 import { eq, sql, and } from "drizzle-orm";
 import { withTransaction } from "@/lib/db";
 import { config } from "@shared/lib/config";
+import { systemEvents, EVENTS } from "@shared/lib/events";
 import type { Transaction } from "@shared/lib/types";
 import { TimerKey, TimerType } from "@shared/lib/constants";
 import { UserError } from "@shared/lib/errors";
@@ -70,8 +71,7 @@ export const levelingService = {
                 .returning();
 
             // Trigger Quest Event
-            const { questService } = await import("@shared/modules/quest/quest.service");
-            await questService.handleEvent(id, 'XP_GAIN', Number(amount), txFn);
+            await systemEvents.emitAsync(EVENTS.DOMAIN.XP_GAINED, { userId: id, amount: Number(amount), tx: txFn });
 
             return { user: updatedUser, levelUp, currentLevel: newLevel };
         }, tx);