Add short game join codes

tests/test_game.py

@@ -443,6 +443,11 @@ def test_game_creation_with_crew_name(session):
     assert game.id is not None
     assert game.crew_name == "The Black Gats"
     assert game.phase == "lobby"
+    assert len(game.join_code) == 5
+    assert set(game.join_code) <= set("ABCDEFGHJKLMNPQRSTUVWXYZ23456789")
+
+    another = crud.create_game(session, crew_name="The Other Gats")
+    assert another.join_code != game.join_code
 
 def test_create_game_endpoint():
     from fastapi.testclient import TestClient
@@ -475,6 +480,17 @@ def test_create_game_endpoint():
         games = session.exec(select(Game)).all()
         assert len(games) == 1
         assert games[0].crew_name == "The Math Mutineers"
+
+        # Codes are case-insensitive at the API boundary and resolve only
+        # active games without exposing the UUID in the code itself.
+        lookup = client.get(f"/api/game/code/{games[0].join_code.lower()}")
+        assert lookup.status_code == 200
+        assert lookup.json() == {"id": games[0].id}
+
+        games[0].phase = "ended"
+        session.add(games[0])
+        session.commit()
+        assert client.get(f"/api/game/code/{games[0].join_code}").status_code == 404
     finally:
         app.dependency_overrides.clear()