chore(server): add vitest as dev dependency with test scripts

Test files existed but vitest wasn't installed. Adds vitest v4,
"test" and "test:watch" scripts. All 22 existing tests pass.

packages/server/package.json

@@ -7,15 +7,17 @@
     "dev": "tsx watch src/index.ts",
     "start": "node --import tsx/esm src/index.ts",
     "build": "tsc",
-    "typecheck": "tsc --noEmit"
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "dependencies": {
+    "@backspace/shared": "workspace:*",
     "@fastify/cors": "^9.0.1",
     "@fastify/multipart": "^8.3.0",
     "@fastify/rate-limit": "^9.1.0",
     "@fastify/static": "^7.0.4",
     "@fastify/websocket": "^10.0.1",
-    "@backspace/shared": "workspace:*",
     "bcryptjs": "^2.4.3",
     "better-sqlite3": "^11.3.0",
     "cheerio": "^1.0.0",
@@ -34,6 +36,7 @@
     "@types/ws": "^8.18.1",
     "drizzle-kit": "^0.24.0",
     "tsx": "^4.16.0",
-    "typescript": "^5.4.0"
+    "typescript": "^5.4.0",
+    "vitest": "^4.0.18"
   }
 }