[US-02] Alternating shooting with feedback

Description

Implements alternating shooting functionality with hit/miss feedback for the Battleship game.

Changes

• Added Game class with turn-based shooting mechanics
• Added ShotResult class to provide feedback on shot outcomes
• Implemented validation to prevent shooting at already-targeted coordinates
• Added comprehensive integration tests covering all acceptance criteria

Acceptance Criteria Verified

✅ When firing at A1 for the first time, a message should appear showing hit or miss, and that field should become marked

• Test: testAcceptanceCriteria_FirstShotAtA1_MessageAndFieldMarked

✅ When the same field is targeted again, the shot should not go through, and the next player should then act

• Test: testAcceptanceCriteria_SameFieldTargetedAgain_ShotRejectedAndTurnAdvances

✅ After one shot cycle finishes, the control changes so that only the other player can continue

• Test: testAcceptanceCriteria_AfterShotCycle_ControlChangesToOtherPlayer

Technical Implementation

• Turn management handled by Game.fireShot() method
• Coordinate validation prevents duplicate shots
• Shot results provide clear hit/miss feedback
• Game state transitions properly between players

Closes #2