test: add deepMerge mock to fix test isolation

Add deepMerge to @shared/lib/utils mocks in both test files to ensure
consistent behavior when tests run together.

web/src/server.items.test.ts

@@ -127,6 +127,7 @@ mock.module("@shared/modules/items/items.service", () => ({
 
 // --- Mock Utilities ---
 mock.module("@shared/lib/utils", () => ({
+    deepMerge: (target: any, source: any) => ({ ...target, ...source }),
     jsonReplacer: (key: string, value: any) =>
         typeof value === "bigint" ? value.toString() : value,
 }));

web/src/server.settings.test.ts

@@ -37,6 +37,13 @@ mock.module("@shared/lib/config", () => ({
     GameConfigType: {}
 }));
 
+// Mock @shared/lib/utils (deepMerge is used by settings API)
+mock.module("@shared/lib/utils", () => ({
+    deepMerge: (target: any, source: any) => ({ ...target, ...source }),
+    jsonReplacer: (key: string, value: any) =>
+        typeof value === "bigint" ? value.toString() : value,
+}));
+
 // Mock BotClient
 const mockGuild = {
     roles: {