Letter Guessing Restrictions Not Enforced

[Hadiqa13]

Reproduction Steps:

1. Start a game with a word like "DOCKER."

2. Guess the letter "D."

3. Try to guess the letter "D" again after it has already been revealed as correct.

Expected Behavior:

1. Once a letter is guessed correctly, it should be disabled and cannot be guessed again during the current round.

Actual Behavior:

1. The same letter can be guessed again even if it has already been guessed correctly.

Severity Level: High

Assigned to: You