test: fill coverage gaps in lobbyService and gameService

- joinLobby: addPlayer returns falsy (race condition fallback)
- joinLobby: lobby disappears between addPlayer and final fetch
- createLobby: non-unique-violation errors re-thrown immediately
- createGameSession: unexpected DB errors propagate correctly

apps/api/src/services/gameService.test.ts

@@ -126,6 +126,14 @@ describe("createGameSession", () => {
 
     expect(mockGetDistractors).toHaveBeenCalledTimes(3);
   });
+
+  it("propagates unexpected errors from getGameTerms", async () => {
+    mockGetGameTerms.mockRejectedValue(new Error("connection refused"));
+
+    await expect(createGameSession(validRequest)).rejects.toThrow(
+      "connection refused",
+    );
+  });
 });
 
 describe("evaluateAnswer", () => {