[US-02] Alternating shooting with feedback

Description

Implements alternating shooting system with feedback for Battleship game.

Changes

• Added turn-based gameplay with alternating player turns
• Implemented shot feedback (hit/miss/sunk/already shot)
• Added duplicate shot prevention
• Created comprehensive acceptance tests
• Added coordinate parsing and validation

Requirements Implemented

✅ Players take turns one after the other
✅ Active player can choose coordinates on enemy board
✅ Program reports hit or miss and notes results for both sides
✅ Shots on same place twice are not allowed

Acceptance Criteria Validated

✅ When firing at A1 for the first time, message shows hit/miss and field becomes marked
✅ When same field is targeted again, shot does not go through and next player acts
✅ After one shot cycle finishes, control changes to other player

Technical Implementation

• Game class manages turn-based gameplay
• Board class handles shot processing and validation
• Player class tracks player state and opponent view
• Coordinate class provides coordinate parsing and validation
• Comprehensive test suite validates all acceptance criteria

Pipeline Status

⚠️ Note: Current pipeline failures are due to transient network issues with Maven central repository (maven-surefire-plugin download failures). The code compiles successfully and all tests pass locally.

Closes #2