test: add comprehensive test suite for server

- Add load testing with Artillery (smoke, standard, peak, stress)
- Add functional tests: voting, lottery, admin (18 tests)
- Add fault tolerance tests (14 tests)
- Add network tests for WebSocket (7 tests)
- Add compatibility tests (15 tests)
- Add security tests: anti-fraud, auth, data integrity (10 tests)
- Fix optional callback handling in socket handlers
- Total: 64 test cases, all passing

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/server/package.json

@@ -13,7 +13,11 @@
     "db:push": "prisma db push",
     "db:seed": "tsx src/scripts/seed.ts",
     "test": "vitest",
-    "test:load": "echo 'Load tests not configured yet'"
+    "test:load": "artillery run load-test/vote-load-test.yaml -e standard",
+    "test:load:smoke": "artillery run load-test/vote-load-test.yaml -e smoke",
+    "test:load:peak": "artillery run load-test/vote-load-test.yaml -e peak",
+    "test:load:stress": "artillery run load-test/vote-load-test.yaml -e stress",
+    "test:load:report": "artillery run load-test/vote-load-test.yaml -e standard --output load-test/report.json && artillery report load-test/report.json"
   },
   "dependencies": {
     "@gala/shared": "workspace:*",
@@ -40,10 +44,12 @@
     "@types/express": "^5.0.0",
     "@types/multer": "^2.0.0",
     "@types/uuid": "^11.0.0",
+    "artillery": "^2.0.28",
     "prisma": "^6.2.1",
+    "socket.io-client": "^4.8.1",
     "tsup": "^8.3.5",
     "tsx": "^4.19.2",
     "typescript": "^5.7.3",
     "vitest": "^2.1.8"
   }
-}
+}