test(api): add unit and integration tests for game service and endpoints

- Unit tests for createGameSession and evaluateAnswer (14 tests)
- Endpoint tests for POST /game/start and /game/answer via supertest (8 tests)
- Mock @glossa/db — no real database dependency

documentation/api-development.md

@@ -313,7 +313,7 @@ Required before: implementing the double join for source language prompt.
 - Central error middleware in `app.ts`
 - Remove temporary `safeParse` error handling from controllers
 
-### Step 7 — Tests
+### Step 7 — Tests - done
 
 - Unit tests for `QuizService` — correct POS filtering, distractor never equals correct answer
 - Unit tests for `evaluateAnswer` — correct and incorrect cases
@@ -339,3 +339,10 @@ Required before: implementing the double join for source language prompt.
   word in the definition text (e.g. "Padre" appearing in the English gloss for
   "father"). Address during the post-MVP data enrichment pass — either clean the
   glosses, replace them with custom definitions, or filter at the service layer. => resolved
+
+-  WARN  2 deprecated subdependencies found: @esbuild-kit/core-utils@3.3.2, @esbuild-kit/esm-loader@2.6.5
+../..                                    | Progress: resolved 556, reused 0, downloaded 0, added 0, done
+ WARN  Issues with peer dependencies found
+.
+└─┬ eslint-plugin-react-hooks 7.0.1
+  └── ✕ unmet peer eslint@"^3.0.0 || ^4.0.0 || ^5.0.0 || ^6.0.0 || ^7.0.0 || ^8.0.0-0 || ^9.0.0": found 10.0.3