feat: scaffold quiz API vertical slice

- Add GameRequestSchema and derived types to packages/shared
- Add SupportedLanguageCode, SupportedPos, DifficultyLevel type exports
- Add getGameTerms() model to packages/db with pos/language/difficulty/limit filters
- Add prepareGameQuestions() service skeleton in apps/api
- Add createGame controller with Zod safeParse validation
- Wire POST /api/v1/game/start route
- Add scripts/gametest/test-game.ts for manual end-to-end testing

apps/api/src/services/gameService.ts

@@ -1,3 +1,16 @@
-export const prepareQuestions = async (params: object) => {
-  console.log(params);
+import type { GameRequestType } from "@glossa/shared";
+import { getGameTerms } from "@glossa/db";
+
+export const prepareGameQuestions = async (gameSettings: GameRequestType) => {
+  const { source_language, target_language, pos, difficulty, rounds } =
+    gameSettings;
+
+  const terms = await getGameTerms(
+    source_language,
+    target_language,
+    pos,
+    difficulty,
+    Number(rounds),
+  );
+  return terms;
 };