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/lib/events.ts

@@ -2,9 +2,22 @@ import { EventEmitter } from "node:events";
 
 /**
  * Global system event bus for cross-module communication.
- * Used primarily for real-time dashboard updates.
+ * Used for real-time dashboard updates and domain event decoupling.
  */
-class SystemEventEmitter extends EventEmitter { }
+class SystemEventEmitter extends EventEmitter {
+    /**
+     * Emit an event and await all listeners sequentially.
+     * Used for domain events that must preserve transaction atomicity
+     * (e.g., quest progress tracking within the caller's DB transaction).
+     */
+    async emitAsync(event: string, ...args: any[]): Promise<boolean> {
+        const listeners = this.listeners(event);
+        for (const listener of listeners) {
+            await (listener as Function)(...args);
+        }
+        return listeners.length > 0;
+    }
+}
 
 export const systemEvents = new SystemEventEmitter();
 
@@ -20,5 +33,16 @@ export const EVENTS = {
     },
     QUEST: {
         COMPLETED: "quest:completed",
-    }
+    },
+    DOMAIN: {
+        BALANCE_CHANGED: "domain:balance_changed",
+        XP_GAINED: "domain:xp_gained",
+        ITEM_COLLECTED: "domain:item_collected",
+        ITEM_USED: "domain:item_used",
+        TRANSFER_COMPLETED: "domain:transfer_completed",
+        DAILY_CLAIMED: "domain:daily_claimed",
+        TRIVIA_STARTED: "domain:trivia_started",
+        TRIVIA_WON: "domain:trivia_won",
+        EXAM_PASSED: "domain:exam_passed",
+    },
 } as const;