Add Test: oracle has_result returns false before submit and true after

[yahia008]

Priority: Low
Estimated Time: 15 minutes

Description:
No test explicitly verifies the has_result function returns false before a result is submitted and true after. The existing test_submit_and_get_result only calls has_result after submission.

Tasks:

• Assert has_result(0) returns false on a fresh contract
• Submit a result for match 0
• Assert has_result(0) returns true