test: add comprehensive test suite for Matches & Ratings API

- Created matches.test.js with 24 tests covering:
  * Match creation and validation
  * Match listing and filtering
  * Match acceptance workflow
  * Match deletion
  * Rating creation and validation
  * User ratings display

- Fixed Jest ES module issues:
  * Added mock for jsdom to bypass parse5 compatibility
  * Added mock for dompurify for test environment
  * Updated package.json with moduleNameMapper

Test results: 19/24 passing (79%)
Remaining: 5 tests need investigation

backend/package.json

@@ -53,7 +53,11 @@
     ],
     "testMatch": [
       "**/__tests__/**/*.test.js"
-    ]
+    ],
+    "moduleNameMapper": {
+      "^jsdom$": "<rootDir>/src/__mocks__/jsdom.js",
+      "^dompurify$": "<rootDir>/src/__mocks__/dompurify.js"
+    }
   },
   "prisma": {
     "seed": "node prisma/seed.js"