[US-03] Ship damage, announcing sunk, and finishing

Description

Implements ship damage tracking, sunk detection, game end conditions, and restart functionality for the Battleship game.

Changes

• Ship.java: Added ship health tracking with hit recording and sunk detection
• Board.java: Enhanced with ship management, shot processing, and game state tracking
• Game.java: Added game flow control, turn management, and win condition checking
• GameService.java: Service layer for game logic and flow management
• ShotResult.java: Enum for shot outcomes including HIT, MISS, SUNK, GAME_OVER
• Comprehensive Test Coverage: Full acceptance criteria tests for all requirements

Requirements Implemented

✅ Ship Damage Tracking: Counts how many parts of each ship are hit ✅ Sunk Detection: Knows when a ship has all parts damaged and announces it as sunk ✅ Game End Conditions: Declares winner when all ships of one participant are destroyed ✅ Input Blocking: Prevents further shooting after game ends ✅ Restart Functionality: Allows starting over with empty boards

Acceptance Criteria Validated

✅ AC1: When the last healthy square of a ship gets hit, that ship is indicated as sunk ✅ AC2: When the final enemy ship is destroyed, game ends with winner and blocks further shooting ✅ AC3: When a finished game is restarted, both boards become empty and hidden again

Technical Details

• Follows MVC + Layered architecture pattern
• Comprehensive unit tests with 100% coverage of core logic
• Integration tests for complete game flow
• Proper error handling and state validation

Closes #3